Question:
home made solar hot water heater I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy. For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated. Alan C — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
home made solar hot water heater
I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy.
Lots of 2 inch round mirrors coms to mind Or you could try silvered mylar and vacuum form it to the dish For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much
Look up “Big Dish” Australian National University . For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best?
Could do. In theory would not exceed 100 Degrees C Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated.
How much lifestyle change can you handle? George Alan C — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
– DON’T PANIC – If in doubt run in circles scream and shout
Response:
- Hide quoted text — Show quoted text – I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy. For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much.
The reason is because for most of the world it is far cheaper to use existing energy sources rather than solar. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me.
My guess is that PV would be practical for most of us when the payback time is somewhere around 5-7 years. Thats about how long most people are willing to invest their unused cash in an attempt to reduce expenses. At 10 cents/kW-hr, and $1/watt for PV costs, the payback time is about 7 years (assuming a grid connection so no battery costs). Since many people pay much less then 10 cents/kW-hr, I’d say the cost would need to come down to more like 50 cents/watt before it could really take off. Some areas with regulatory problems that have created artificially high electrical costs (such as California) would obviously have a different price point, although a change in political philosophy might take place that would be far more cost effective for most consumers. $0.10 kW-hr cost of electricity $1.00 PV watt cost 4 hours per day of usable sunlight 0.0040 kw-hr/day/watt of PV capacity $0.15 value of electricity/year 6.85 years payback Of course reducing demand in one area of the country, would reduce the cost of existing electricity in the rest of the country. Due to stupidity of the utility regulators, who tried to reduce cost by restricting supply, there is little extra supply, thus costs will remain relatively high. If supply increases, costs will drop in a free market. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated. Alan C
C$3500/year is only about USD$2200/year. Thats less than $200 per month for all your energy needs. Its probably about what most people around here pay in combined gas and electric. You must have relatively cheap electric rates. You might want to look at some of the simpler things before jumping on the solar bandwagon. Canada has less sunlight, thus what works well in Arizona may not be as efficient where you are. A good start would be to look at things like how well your windows work. Its amazing how much energy can be saved by getting rid of outdated windows and putting in new ones. A lot more comfortable as well. Vinyl replacement windows are available for around $100-150 each to replace any old beaters. Check for air infiltration at outlet boxes on outside walls. Cheap fixes are available at your local home store. $1 or so for a gasket to keep the cold air from seeping into your home. Check your attic. Additional insulation may be cost effective. Hot water heater blankets may be useful, although the little bit of heat saved may not be worth what the blanket costs for more modern water heaters. Ceiling fans can make a huge difference in the amount of AC you need to stay cool in the summer. Setback thermostats work well at reducing heating load. Zoned heating is a good idea if you don’t already have it. Why heat a bedroom all day when you are only in that room at night. Don’t heat the living room during the night when no one is in that room.
Response:
I think this approach to the problem misses a few major issues. First, most of us know that the cost of power is going to inflate over the next 10 years, and there is a lot of uncertainty over just how fast or how far it inflates. This argues for buying the insurance before the death, so to speak. We would pay a modest premium today for power at a fixed price in 10 years. Unfortunately, it is not really that simple. First off, we need that battery pack somewhere. Wouldn’t you feel the fool to pay a premium for solar in 10 years, and then see your grid connection scarf up all of your “savings” when the time comes and they have to buy so many batteries to cover the PV. Second, this distant future ( how many of us know we will have jobs in a year, much less be living in this house in 10 years) will be able to sell us power made by PVs as easily as we can buy them today, perhaps cheaper, and we would not then have to hold the large and empty money bag. Share the risk, share the benefit. And lastly, as long as this is a private PV enterprise, it gets the same care the house siding gets and can be sold when we have to move for just what any other wonderful addition to a house can be sold for. Just about nothing if folk aren’t slavering for it. We might make some big differences if we could solve the battery problem, get homeowner groups to support solar in their communities with group maintenance and storage and agreements to keep new folk interested in supporting the effort even if they are technically incompetent and don’t see the big picture. Anyone can see the $100 a month electric production benefit, and it needs to come down to that I think. .
home made solar hot water heater
Response:
Newsgroups: alt.energy.homepower, alt.energy.renewable, alt.solar.photovoltaic, alt.solar.thermal I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy.
Alan, I am working on a similar project and have had the same questions. Right now my dish is the perforated aluminum type. I think it would be okay to use whatever dish is available. The plan is to line the dish with triangular pieces of reflective mylar. This can be purchased in rolls from some hardware, greenhouse, or other stores. Another way to go would be to use aluminum foil – crude, I know, but cheap and commonly available. A third idea is to use 10000 +/- discarded CDs that are scratched, cracked, or otherwise JUNK. Those would reflect well, and each CD could be independently aimed for maximum accuracy. You could do the same aiming technique with pieces of mylar glued to little bits of wood of cardboard. When you surfed around on the web, I wonder if you noticed any free plans for unlimited-size solar thermal arrays. The common version starts with a planar surface, like a piece of plywood. Then however many reflectors are desired – you could use pieces of a broken mirror, bottoms of aluminum cans, reflecting shards of polished ice … whatever you have, in any size shape, form, or quantity, attach them to the board. As each one is attached, aim them at the target. Of course, the sun is moving while you do this, so correct for this variation. Viola! Infinitely-adjustable size solar thermal grid. The best idea IMHO is to put evenly spaced nails in two perpendicular boards, fixed in the form of a capital “L.” Then string the nails to form a perfect parabola of the desired size. Again with this method, small reflectors are adjusted one at a time and aimed to hit the target. I was thinking of using a dish in the center, and big flat-array panels around the dish, like petals on a big shiny flower. These ‘petals’ would be hinged, for temperature control and transportation / night storage purposes. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt
I encourage you to go ahead and try it. I am highly confident you will have great success if you construct such a device. Please keep me & the newsgroup informed as this progresses. Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned? Any comments would be much appreciated. Alan C
Steam generators are a proven technology. In my opinion that is a fairly safe way to generate electricity (compared to fossil fuels, nuclear, et cetera). I think you are onto something when you ask if a steel boiler at the focus may be best. Some things I know about using water to store heat: water is not expensive. Water mitigates temperature change – it has a lot of thermal mass compared to some substances. Water is easy to move in case you must adjust the amount of storage capacity. The metric system is designed to make your calculations easy if you use water. Good luck with your project. - Andy P.S. If a lot of your high bills are related to heating your home, I would also nominate the following solution. There are passive solar heated houses and greenhouses that use big black barrels of water to catch and radiate heat. http://www.botanic.org/ has more information about one such place near my home. There are many other examples.
Response:
A third idea is to use 10000 +/- discarded CDs that are scratched, cracked, or otherwise JUNK. Those would reflect well, and each CD could be independently aimed for maximum accuracy. You could do the same aiming technique with pieces of mylar glued to little bits of wood of cardboard.
I’m not sure cds are stable in sunlight. I think they are polycarbonate and I have a greenhouse catalog that sells GE lexan PC and they have a big warning about getting the UV resistant coating right side up or the PC will be damaged. So it sounds like PC isn’t intrinsically UV resistant. I know PC is made for glazing so it’s either coated or a special formulation and music cds might not be. HTH
Response:
Many thanks to all who have taken the trouble to reply so far. Lots of good ideas to be considered. BTW “all electric” did mean including heating. I live near Ottawa, Canada. Power costs, at present, about 10 C per kWh. Last year I used 32183 kWh!! My initial, very interim, conclusion, from simple cost/payback analyses, suggests the dish idea is a complete bust. It could pay itself back in 2 or 3 years, which is good, but would only produce maybe $200 worth of energy per year. A much bigger device was ably described by Wayne Roderick at http://www.ida.net/users/tetonsl/solar/page_i.htm. He calculated that this was worth about $420 (US) per year to him at a power cost of only 3 C per kWh. An interesting experiment but not worth enough for me to bother with, except for fun. PV is nowhere close to be worth considering at all (for my case) and probably won’t be for many years. This has been true for many years. Funny that!! Improving my insulation is essential and I’ll start immediately. Flat plate heat collectors are likely worthwhile but they won’t work well on really cold days here. We occasionally go down to -40 degrees at night with day time temps at 0 F (-17 C). Increasing the number of layers of glass may help but increases cost and reduces actual solar input so there must be a limit to this approach. Maybe augmenting this with a heat pump would be beneficial. I could get air conditioning out of this too. Wind power is just possible here but I can’t justify adequate battery storage. Dumping the energy into the warm water store bears further investigation I think. If I could put excess wind powered energy into the power grid and run my meter backwards I think I’d have a good case for a fairly big machine. Thanks again Folks. I’ll keep you informed as to what I decide and actually do (if anything, beyond insulating a lot). I’m happy to have found this group.
I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect
home made solar hot water heater
There are several assumptions that are based on politics rather than economics or science in your post. First off, there is no guarantee that electric power will cost more in ten years than it does today. In fact, it may well go down. The main reason for power prices spiking in many states has been the bizarre policy of state regulators attempting to reduce prices by restricting supplies. Any one that believes this is an effective long term strategy needs to get his/her head examined. Much of the reason for the attempts to restrict supply is supposedly for environmental reasons. This is pretty laughable on its face, and I won’t go into the many reasons, but suffice it to say that large scale fossil fuel power production is far less damaging to the environment than many small scale plants. Its practical and economical today for smaller scale hydro plants to be installed in thousands of places, yet “environmentalists” block any attempt to do so. Hydro produces zero pollution and generally creates additional recreational water space, which one would think the enviros would be in favor of. One must always keep in mind that what they are really opposed to is free market capitalism. Look at the rhetoric and this conclusion is irrefutable. Another safe, non-polluting source of electrical energy that has a lot of opposition from the green crowd is nuclear. Nuclear is about as green as you can get. The fuel can be recycled (except for the greenie opposition to doing so) and the little bit left over that can’t be recycled can be dumped far underground where it is quite safe, or dumped in the oceans where it can be diluted to the point of background noise (probably the safest and best longterm solution). Home generated power is probably never going to be much more than a curiousity for most of us, unless our lifestyle dictates it, or we take it up as a hobby, at least with the current generating means at our disposal. The fact is that most people live in urban areas (many in apartments and condos) where there is no place to physically locate PV panels, or other power generating equipment, even technologies like fuel cells take up space that just does not exist for them in most people’s domiciles.
Response:
<<<orignal post snipped The idea of using an abandoned C band satellite dish as a solar collector has been around a long time. I’d be willing to bet you could do a google search and find people who have tried it. I suspect as a means of heating up water it may well be practical, maybe even beating out roof mounted solar collectors. Most of the people I have read about who have tried it used some kind of mylar film as a reflective medium. Never having tried it myself, I don’t know if this is the “best” way to go, only that it seems do-able. I dount you will be able to generate any electrical power from such a contraption though. Small scale steam engines or turbines are not practical for electrical generation, but it might work Ok as a hot water heater. If you enjoy tinkering, you might find it an interesting project. home made solar hot water heater
Response:
Comments under Bob’s
I think this approach to the problem misses a few major issues…. There are several assumptions that are based on politics rather than economics or science in your post. First off, there is no guarantee that electric power will cost more in ten years than it does today.
Quite correct. in 10 years we may hope that practical fusion power will flood the market. Well, perhaps that is more likely in 20? Wait, we have already spent several billions on development, and today can project a plant that would be so much larger than anything built yet that it’s gravity would have to be added to the confinement forces. Perhaps we should count that as a long shot for even 100 years. We could have a catastrophic new flu, and loose half the human race. We could finally decide fission plants are cute and build one in every large town, using the waste heat for winter heating. Or we could have a beer and wait it out, and we can expect the average price for base power to increase by 3-5% a year in the good years. There is a risk that the inflation rate will be much higher, or that deflation will occure in this area, but the expected result of do nothing is to see the inflation. This is not politics, and I am puzzled why you imagine it is. It is a reasonable expectation based on history, with uncertainties which are independant of politics, but which politics may chose to evaluate differently. Its practical and economical today for smaller scale hydro plants to be installed in thousands of places, yet “environmentalists” block any attempt to do so. Hydro produces zero pollution and generally creates additional recreational water space, which one would think the enviros would be in favor of. One must always keep in mind that what they are really opposed to is free market capitalism. Look at the rhetoric and this conclusion is irrefutable.
Free market capitalism? I have lived in the US all my life and never seen any of this. Heard lots of talk, and seen catastrophe after catastrophe result from letting capital run after the power structure in this country. Well, to each his own. However, Zero pollution is not at all what a dam produces. You know that. Why do you ignore it? Every dam has impacts on the down streamers. Some minor, some positive, and some very negative. It is not a minor impact on the fish populations. The warmer water changes the trout survival rates and will effect game fishing dramatically. The lack of flooding is good, if you live on the stream, but bad if the stream delta is a wet land and provides for nesting birds and breeding fish. We could be killing ourselves by reducing our own fish populations with the very dams that give us power and water. So are you going to figure out who’s livelihood is to be sacrificed to build, or to tear down a dam? This is not an environmental loony, versus a virtuous free market capitalist. At least I don’t think it is. I like irrefutable. But I think this is a refutable conclusion. No one cares about free market capitalism but the capitalist zealots because there is no such thing, and no one wants it, and it’s Enrons, in their own back yard. Worst than the nukes I expect.
Response:
for dish based solar hot water systems, see http://webconx.green-trust.org/2000/solar/acro.htm — Steve Spence Subscribe to the Renewable Energy Newsletter & Discussion Boards. Read about Sustainable Technologyhome made solar hot water heaterhome made solar hot water heater
name a few.
- Hide quoted text — Show quoted text – There are several assumptions that are based on politics rather than economics or science in your post. One must always keep in mind that what they are really opposed to is free market capitalism. Look at the rhetoric and this conclusion is irrefutable. Some of the most extreme environmentalists are also very successful industrial capitalists. In a word, you’re wrong.
Response:
<<<orignal post snipped The idea of using an abandoned C band satellite dish as a solar collector has been around a long time. I’d be willing to bet you could do a google search and find people who have tried it. I suspect as a means of heating up water it may well be practical, maybe even beating out roof mounted solar collectors. Most of the people I have read about who have tried it used some kind of mylar film as a reflective medium. Never having tried it myself, I don’t know if this is the “best” way to go, only that it seems do-able. I dount you will be able to generate any electrical power from such a contraption though. Small scale steam engines or turbines are not practical for electrical generation, but it might work Ok as a hot water heater. If you enjoy tinkering, you might find it an interesting project.
Response:
I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy. For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated. Alan C — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
Response:
- Hide quoted text — Show quoted text – I think this approach to the problem misses a few major issues. First, most of us know that the cost of power is going to inflate over the next 10 years, and there is a lot of uncertainty over just how fast or how far it inflates. This argues for buying the insurance before the death, so to speak. We would pay a modest premium today for power at a fixed price in 10 years. Unfortunately, it is not really that simple. First off, we need that battery pack somewhere. Wouldn’t you feel the fool to pay a premium for solar in 10 years, and then see your grid connection scarf up all of your “savings” when the time comes and they have to buy so many batteries to cover the PV. Second, this distant future ( how many of us know we will have jobs in a year, much less be living in this house in 10 years) will be able to sell us power made by PVs as easily as we can buy them today, perhaps cheaper, and we would not then have to hold the large and empty money bag. Share the risk, share the benefit. And lastly, as long as this is a private PV enterprise, it gets the same care the house siding gets and can be sold when we have to move for just what any other wonderful addition to a house can be sold for. Just about nothing if folk aren’t slavering for it. We might make some big differences if we could solve the battery problem, get homeowner groups to support solar in their communities with group maintenance and storage and agreements to keep new folk interested in supporting the effort even if they are technically incompetent and don’t see the big picture. Anyone can see the $100 a month electric production benefit, and it needs to come down to that I think. .
There are several assumptions that are based on politics rather than economics or science in your post. First off, there is no guarantee that electric power will cost more in ten years than it does today. In fact, it may well go down. The main reason for power prices spiking in many states has been the bizarre policy of state regulators attempting to reduce prices by restricting supplies. Any one that believes this is an effective long term strategy needs to get his/her head examined. Much of the reason for the attempts to restrict supply is supposedly for environmental reasons. This is pretty laughable on its face, and I won’t go into the many reasons, but suffice it to say that large scale fossil fuel power production is far less damaging to the environment than many small scale plants. Its practical and economical today for smaller scale hydro plants to be installed in thousands of places, yet “environmentalists” block any attempt to do so. Hydro produces zero pollution and generally creates additional recreational water space, which one would think the enviros would be in favor of. One must always keep in mind that what they are really opposed to is free market capitalism. Look at the rhetoric and this conclusion is irrefutable. Another safe, non-polluting source of electrical energy that has a lot of opposition from the green crowd is nuclear. Nuclear is about as green as you can get. The fuel can be recycled (except for the greenie opposition to doing so) and the little bit left over that can’t be recycled can be dumped far underground where it is quite safe, or dumped in the oceans where it can be diluted to the point of background noise (probably the safest and best longterm solution). Home generated power is probably never going to be much more than a curiousity for most of us, unless our lifestyle dictates it, or we take it up as a hobby, at least with the current generating means at our disposal. The fact is that most people live in urban areas (many in apartments and condos) where there is no place to physically locate PV panels, or other power generating equipment, even technologies like fuel cells take up space that just does not exist for them in most people’s domiciles.
Response:
Many thanks to all who have taken the trouble to reply so far. Lots of good ideas to be considered. BTW “all electric” did mean including heating. I live near Ottawa, Canada. Power costs, at present, about 10 C per kWh. Last year I used 32183 kWh!! My initial, very interim, conclusion, from simple cost/payback analyses, suggests the dish idea is a complete bust. It could pay itself back in 2 or 3 years, which is good, but would only produce maybe $200 worth of energy per year. A much bigger device was ably described by Wayne Roderick at http://www.ida.net/users/tetonsl/solar/page_i.htm. He calculated that this was worth about $420 (US) per year to him at a power cost of only 3 C per kWh. An interesting experiment but not worth enough for me to bother with, except for fun. PV is nowhere close to be worth considering at all (for my case) and probably won’t be for many years. This has been true for many years. Funny that!! Improving my insulation is essential and I’ll start immediately. Flat plate heat collectors are likely worthwhile but they won’t work well on really cold days here. We occasionally go down to -40 degrees at night with day time temps at 0 F (-17 C). Increasing the number of layers of glass may help but increases cost and reduces actual solar input so there must be a limit to this approach. Maybe augmenting this with a heat pump would be beneficial. I could get air conditioning out of this too. Wind power is just possible here but I can’t justify adequate battery storage. Dumping the energy into the warm water store bears further investigation I think. If I could put excess wind powered energy into the power grid and run my meter backwards I think I’d have a good case for a fairly big machine. Thanks again Folks. I’ll keep you informed as to what I decide and actually do (if anything, beyond insulating a lot). I’m happy to have found this group.
I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect
and — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
Response:
I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity.
Why not look at the calculation? An 8 foot diameter dish is about 50.25 ft^2. Multiply by .0929 to get square meters gives 4.67 m^2. http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/ This site from NREL has solar information. It shows average daily solar radiation for a two axis tracking concentrator as anywhere from 3 to 7 kWh/m^2/day, depending on location in the United States. You mentioned you were in Canada so I’d say you’re probably going to get less than 4 kWh/m^2/day. 4.67 m^2 * 4 kWh/m^2/day = 18.68 kWh/day. So far, so good. Then you have to figure how reflective your mirrors are going to be. I’ve heard 3M came out with a multilayer mirror that is over 99% but typically the best silver surface mirrors seem to run about 95% and normal mylar from 80% to 90%. This makes it more like 16 kWh/day. Then you have to figure conversion inefficiency. Normal PV cells are about 15% efficient even though there are some experimental cells that have got over 35%. Solar thermal can do as much as 20%+ but only on a massive scale. A small thermal engine will have much higher losses. I’ve heard getting as much as 5% can be a challenge on home built equipment of this scale. This would include the generator losses as well. So, let’s say you can convert 10% (optimistic). This turns your 16 kWh/day into 1.6 kWh/day of electricity. This is still respectable but it’s an order of magnitude less than the numbers you were looking at. If you can only get 5% then you’re talking .8 kWh/day. I would appreciate advice as to how best to silver the dish as well as how to transform the energy.
I’ve heard of people breaking up mirrors or mirror tiles and sticking the pieces to the dish. I’ve heard of others using mylar and sticking that on with glue, axle grease or something of that sort. You can probably take it to a auto place and have it chromed if you like. For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much.
Concentrator solar cells are more expensive but they can be found, I think. Regular cells don’t seem to like much more than a few suns but it’s not the sunlight that gets them, it’s the heat. You’ll need some kind of cooling system for PV of any kind when used with this kind of reflector. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me.
Economics isn’t so very simple. What if your electricity cost from the grid doubled or even tripled? I’ve seen electricity costs do exactly this here in California in a single year. What will happen in over 20 years? Just to muddy the waters a little more, many locations are offering various rebate, buydown and tax incentive programs to help offset the cost. http://www.ecobusinesslinks.com/links/solar_panel_price_surveys.htm The best price for PV panels I’ve seen is $3.25/watt for off-spec ASE panels and about $3.75 for normal panels. In a typical grid tied PV system the PV panels themselves only make up from 40% to 60% of the total cost. Inverters, mounts, wiring, labor and all the rest can cost as much or more than the panels themselves. Labor alone can be 20% to 30% of the system cost so if you do the work yourself you should be able to see some significant savings. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day?
Hmm, you’ve got 4.67 m^2 of dish and the sunlight you can focus is (guessing) probably less than 900 W/m^2 and you’re only going to be able to convert, say, 10% of that sunlight so you’re only talking about 420 watts max. Maybe only as much as 200 watts, depending on your engines efficiency. Would a simple steel “boiler” at the focus be best?
You could try the redrok site. http://www.redrok.com/main.htm I think I saw something about a flash boiler using a copper tube spiral embedded in a cast aluminum block. Is storing energy as hot water the best way to go as far as overall economy is concerned.
Storing energy all depends on what you want to do with that energy. Storing heat (thermal) is very good if the energy you need is heat. It’s only so-so if you need it later to run a steam turbine. The economics of it all will depend on how much it costs you. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon.
Well, the most efficient and economical thing to do would be to install solar thermal air heating. These can be home made as flat panels attached to the south side of your house out of parts available at almost any home improvement or hardware store and cost very little. Next most economical is to cut down on your electricity use. Start cooking with sunlight, replace incandescent bulbs with fluorescent lights, buy a better fridge or freezer, weather-strip and stop up all the drafts in your house, install more or better insulation, turn things off when you’re not using them, get rid of phantom loads, etc. You might want to explore a wood, pellet, corn, propane, natural gas or oil burning furnace as well. Next most economical is to build yourself some solar water heater stuff. These can be used to pre-heat the water going into your existing water heater. If they work well enough you can either turn your water heater thermostat down or off entirely. Then you might want to explore wind energy. If you have the space and the wind then this can be much more economical than solar. You could also explore microhydro but you would need some kind of running water on your property to do this. Anthony
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Newsgroups: alt.energy.homepower, alt.energy.renewable, alt.solar.photovoltaic, alt.solar.thermal I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy.
Alan, I am working on a similar project and have had the same questions. Right now my dish is the perforated aluminum type. I think it would be okay to use whatever dish is available. The plan is to line the dish with triangular pieces of reflective mylar. This can be purchased in rolls from some hardware, greenhouse, or other stores. Another way to go would be to use aluminum foil – crude, I know, but cheap and commonly available. A third idea is to use 10000 +/- discarded CDs that are scratched, cracked, or otherwise JUNK. Those would reflect well, and each CD could be independently aimed for maximum accuracy. You could do the same aiming technique with pieces of mylar glued to little bits of wood of cardboard. When you surfed around on the web, I wonder if you noticed any free plans for unlimited-size solar thermal arrays. The common version starts with a planar surface, like a piece of plywood. Then however many reflectors are desired – you could use pieces of a broken mirror, bottoms of aluminum cans, reflecting shards of polished ice … whatever you have, in any size shape, form, or quantity, attach them to the board. As each one is attached, aim them at the target. Of course, the sun is moving while you do this, so correct for this variation. Viola! Infinitely-adjustable size solar thermal grid. The best idea IMHO is to put evenly spaced nails in two perpendicular boards, fixed in the form of a capital “L.” Then string the nails to form a perfect parabola of the desired size. Again with this method, small reflectors are adjusted one at a time and aimed to hit the target. I was thinking of using a dish in the center, and big flat-array panels around the dish, like petals on a big shiny flower. These ‘petals’ would be hinged, for temperature control and transportation / night storage purposes. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt
I encourage you to go ahead and try it. I am highly confident you will have great success if you construct such a device. Please keep me & the newsgroup informed as this progresses. Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned? Any comments would be much appreciated. Alan C
Steam generators are a proven technology. In my opinion that is a fairly safe way to generate electricity (compared to fossil fuels, nuclear, et cetera). I think you are onto something when you ask if a steel boiler at the focus may be best. Some things I know about using water to store heat: water is not expensive. Water mitigates temperature change – it has a lot of thermal mass compared to some substances. Water is easy to move in case you must adjust the amount of storage capacity. The metric system is designed to make your calculations easy if you use water. Good luck with your project. - Andy P.S. If a lot of your high bills are related to heating your home, I would also nominate the following solution. There are passive solar heated houses and greenhouses that use big black barrels of water to catch and radiate heat. http://www.botanic.org/ has more information about one such place near my home. There are many other examples.
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I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy.
Lots of 2 inch round mirrors coms to mind Or you could try silvered mylar and vacuum form it to the dish For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much
Look up “Big Dish” Australian National University . For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best?
Could do. In theory would not exceed 100 Degrees C Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated.
How much lifestyle change can you handle? George Alan C — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
– DON’T PANIC – If in doubt run in circles scream and shout
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I think this approach to the problem misses a few major issues. First, most of us know that the cost of power is going to inflate over the next 10 years, and there is a lot of uncertainty over just how fast or how far it inflates. This argues for buying the insurance before the death, so to speak. We would pay a modest premium today for power at a fixed price in 10 years. Unfortunately, it is not really that simple. First off, we need that battery pack somewhere. Wouldn’t you feel the fool to pay a premium for solar in 10 years, and then see your grid connection scarf up all of your “savings” when the time comes and they have to buy so many batteries to cover the PV. Second, this distant future ( how many of us know we will have jobs in a year, much less be living in this house in 10 years) will be able to sell us power made by PVs as easily as we can buy them today, perhaps cheaper, and we would not then have to hold the large and empty money bag. Share the risk, share the benefit. And lastly, as long as this is a private PV enterprise, it gets the same care the house siding gets and can be sold when we have to move for just what any other wonderful addition to a house can be sold for. Just about nothing if folk aren’t slavering for it. We might make some big differences if we could solve the battery problem, get homeowner groups to support solar in their communities with group maintenance and storage and agreements to keep new folk interested in supporting the effort even if they are technically incompetent and don’t see the big picture. Anyone can see the $100 a month electric production benefit, and it needs to come down to that I think. .
- Hide quoted text — Show quoted text – I have a disused 8 ft diameter C Band antenna … … My guess is that PV would be practical for most of us when the payback time is somewhere around 5-7 years. Thats about how long most people are willing to invest their unused cash in an attempt to reduce expenses. At 10 cents/kW-hr, and $1/watt for PV costs, the payback time is about 7 years (assuming a grid connection so no battery costs). Since many people pay much less then 10 cents/kW-hr
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Comments under Bob’s
I think this approach to the problem misses a few major issues…. There are several assumptions that are based on politics rather than economics or science in your post. First off, there is no guarantee that electric power will cost more in ten years than it does today.
Quite correct. in 10 years we may hope that practical fusion power will flood the market. Well, perhaps that is more likely in 20? Wait, we have already spent several billions on development, and today can project a plant that would be so much larger than anything built yet that it’s gravity would have to be added to the confinement forces. Perhaps we should count that as a long shot for even 100 years. We could have a catastrophic new flu, and loose half the human race. We could finally decide fission plants are cute and build one in every large town, using the waste heat for winter heating. Or we could have a beer and wait it out, and we can expect the average price for base power to increase by 3-5% a year in the good years. There is a risk that the inflation rate will be much higher, or that deflation will occure in this area, but the expected result of do nothing is to see the inflation. This is not politics, and I am puzzled why you imagine it is. It is a reasonable expectation based on history, with uncertainties which are independant of politics, but which politics may chose to evaluate differently. Its practical and economical today for smaller scale hydro plants to be installed in thousands of places, yet “environmentalists” block any attempt to do so. Hydro produces zero pollution and generally creates additional recreational water space, which one would think the enviros would be in favor of. One must always keep in mind that what they are really opposed to is free market capitalism. Look at the rhetoric and this conclusion is irrefutable.
Free market capitalism? I have lived in the US all my life and never seen any of this. Heard lots of talk, and seen catastrophe after catastrophe result from letting capital run after the power structure in this country. Well, to each his own. However, Zero pollution is not at all what a dam produces. You know that. Why do you ignore it? Every dam has impacts on the down streamers. Some minor, some positive, and some very negative. It is not a minor impact on the fish populations. The warmer water changes the trout survival rates and will effect game fishing dramatically. The lack of flooding is good, if you live on the stream, but bad if the stream delta is a wet land and provides for nesting birds and breeding fish. We could be killing ourselves by reducing our own fish populations with the very dams that give us power and water. So are you going to figure out who’s livelihood is to be sacrificed to build, or to tear down a dam? This is not an environmental loony, versus a virtuous free market capitalist. At least I don’t think it is. I like irrefutable. But I think this is a refutable conclusion. No one cares about free market capitalism but the capitalist zealots because there is no such thing, and no one wants it, and it’s Enrons, in their own back yard. Worst than the nukes I expect.
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You are welcome. You might look at Thermomax or Swingsys evacuated tube solar thermal collectors. They use them in colder climates. http://www.thermomax-group.com http://www.swingsys.com/
home made solar hot water heater
[ snip snip ] Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated.
When you say “all electric”, and your annual electricity bill is $3500, I assume that your house is heated by electricity. Correct? If that is the case, the quickest way to reduce your energy cost is to switch to a different source of energy for heating your house: natural gas (probably not available, or you would be using it), propane, oil, wood, or sunshine. Any of these options will have a much lower annual cost than your current electric heating. If there are no ducts in your house for forced air heating, then consider installing in-floor heating — generally said to be more efficient, and keeps a room feeling comfortable without blowing a lot of dust around. Depending on where in Canada you live, you might also look at adding some active solar heating. Where I live (in Southern Ontario) we generally get very little sunshine during the coldest months. However, I understand that in Manitoba there is lots of sunshine in the winter months. It is *much* easier to convert the sun’s rays into heat than into electricity. Since heating is the biggest part of your energy costs, you should focus (clever pun, eh? 
on supplying the heat you need rather than the electricity you’re currently paying for. Regards, Bert Menkveld (Currently averaging about 6 to 7 KWh/day in electricity consumption).
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Many thanks to all who have taken the trouble to reply so far. Lots of good ideas to be considered. BTW “all electric” did mean including heating. I live near Ottawa, Canada. Power costs, at present, about 10 C per kWh. Last year I used 32183 kWh!! My initial, very interim, conclusion, from simple cost/payback analyses, suggests the dish idea is a complete bust. It could pay itself back in 2 or
If you use your dish to send the sunlight into the house, then you have a high efficiency solar heater capable of a peak output of a few kilowatts of heat. Be warned that is a whole lot of heat, more than enough to set fire to something, so you must have nothing flammable in the light path, including the path the light would go if the dish stopped moving due to failure. You’d also need a thermostat conected to the tracker to point it elsewhere when things got hot. A tracker and some fireproofing might not cost too much, it probably would pay its way many times over, just take the fire aspect fully seriously. Also running a heat pump on electric is a third or a quarter the running cost of straight electric heating. When it really pays well is if you can pick up an old commercial freezer / fridge unit for peanuts. New units are costly. With the old refrigeration units, as long as the compressor runs the rest can be made to work. All the controls, fans etc can be frazzled, and it can still be got working. Flat plate heat collectors are likely worthwhile but they won’t work well on really cold days here. We occasionally go down to -40 degrees at night with day time temps at 0 F (-17 C). Increasing the number of layers of glass may help but increases cost and reduces actual solar input so there must be a limit to this approach.
Low level concentration helps a lot. Its not too hard to put say 2 to 3 suns onto the collectors. Wind power is just possible here but I can’t justify adequate battery storage. Dumping the energy into the warm water store bears further investigation I think.
The numbers are monstrously bad. Thanks again Folks. I’ll keep you informed as to what I decide and actually do (if anything, beyond insulating a lot). I’m happy to have found this group.
Yep, superinsulation is your friend. Regards, NT
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A third idea is to use 10000 +/- discarded CDs that are scratched, cracked, or otherwise JUNK. Those would reflect well, and each CD could be independently aimed for maximum accuracy. You could do the same aiming technique with pieces of mylar glued to little bits of wood of cardboard.
I’m not sure cds are stable in sunlight. I think they are polycarbonate and I have a greenhouse catalog that sells GE lexan PC and they have a big warning about getting the UV resistant coating right side up or the PC will be damaged. So it sounds like PC isn’t intrinsically UV resistant. I know PC is made for glazing so it’s either coated or a special formulation and music cds might not be. HTH
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- Hide quoted text — Show quoted text – I have a disused 8 ft diameter C Band antenna with a solid dish (not perforated). Initial calculations show that I should be able to collect and concentrate quite a reasonable amount of energy with this thing (10 to 20 kWhr per day) if I add a vertical movement capability (easy I think), apply a reflective surface and find a way to transform the concentrated sunlight into electricity. I would appreciate advice as to how best to silver the dish as well as how to transform the energy. For example how many times concentration can a solar PV panel or a concentrating solar cell tolerate? What are the sizes of concentrating solar cells so I can estimate the size I need at the focus? How efficient are these things? What do they cost and where might I find more information on them? I can only find vague statements to the effect that they are wonderful and will change the World, later! Such statements have appeared for years and we don’t seem to be progressing much.
The reason is because for most of the world it is far cheaper to use existing energy sources rather than solar. For what it is worth (I’m new to this) I believe we must be able to transform light into electricity for much less than $1 per Watt before PV becomes worthwhile for locations which have access to mains electricity. The best price I have seen is around $5 per Watt so this is not viable for me.
My guess is that PV would be practical for most of us when the payback time is somewhere around 5-7 years. Thats about how long most people are willing to invest their unused cash in an attempt to reduce expenses. At 10 cents/kW-hr, and $1/watt for PV costs, the payback time is about 7 years (assuming a grid connection so no battery costs). Since many people pay much less then 10 cents/kW-hr, I’d say the cost would need to come down to more like 50 cents/watt before it could really take off. Some areas with regulatory problems that have created artificially high electrical costs (such as California) would obviously have a different price point, although a change in political philosophy might take place that would be far more cost effective for most consumers. $0.10 kW-hr cost of electricity $1.00 PV watt cost 4 hours per day of usable sunlight 0.0040 kw-hr/day/watt of PV capacity $0.15 value of electricity/year 6.85 years payback Of course reducing demand in one area of the country, would reduce the cost of existing electricity in the rest of the country. Due to stupidity of the utility regulators, who tried to reduce cost by restricting supply, there is little extra supply, thus costs will remain relatively high. If supply increases, costs will drop in a free market. Are there yet any economical Sterling engines or something similar which are capable of being mounted at the focal point and of generating a Kilowatt or so for 5 or 6 hours on a sunny day? Would a simple steel “boiler” at the focus be best? Is storing energy as hot water the best way to go as far as overall economy is concerned. I live in Canada and my house is “all electric”. My power Bill is nearly $3500 per year so I do have a powerful incentive to do something and do it soon. Any comments would be much appreciated. Alan C
C$3500/year is only about USD$2200/year. Thats less than $200 per month for all your energy needs. Its probably about what most people around here pay in combined gas and electric. You must have relatively cheap electric rates. You might want to look at some of the simpler things before jumping on the solar bandwagon. Canada has less sunlight, thus what works well in Arizona may not be as efficient where you are. A good start would be to look at things like how well your windows work. Its amazing how much energy can be saved by getting rid of outdated windows and putting in new ones. A lot more comfortable as well. Vinyl replacement windows are available for around $100-150 each to replace any old beaters. Check for air infiltration at outlet boxes on outside walls. Cheap fixes are available at your local home store. $1 or so for a gasket to keep the cold air from seeping into your home. Check your attic. Additional insulation may be cost effective. Hot water heater blankets may be useful, although the little bit of heat saved may not be worth what the blanket costs for more modern water heaters. Ceiling fans can make a huge difference in the amount of AC you need to stay cool in the summer. Setback thermostats work well at reducing heating load. Zoned heating is a good idea if you don’t already have it. Why heat a bedroom all day when you are only in that room at night. Don’t heat the living room during the night when no one is in that room.
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for dish based solar hot water systems, see http://webconx.green-trust.org/2000/solar/acro.htm — Steve Spence Subscribe to the Renewable Energy Newsletter & Discussion Boards. Read about Sustainable Technology: http://www.green-trust.org
home made solar hot water heater. I’d be willing to bet you could do a google search and find people who have tried it. I suspect as a means of heating up water it may well be practical, maybe even beating out roof mounted solar collectors. Most of the people I have read about who have tried it used some kind of mylar film as a reflective medium. Never having tried it myself, I don’t know if this is the “best” way to go, only that it seems do-able. I dount you will be able to generate any electrical power from such a contraption though. Small scale steam engines or turbines are not practical for electrical generation, but it might work Ok as a hot water heater. If you enjoy tinkering, you might find it an interesting project. home made solar hot water heater
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