froggy:also, if everyone doesnt already know this...solar heating is by far the most cost effective way to go renewable. so it seems the cost to that part of the system is already low. seems like an easy marriage, what am i missing?
also, if everyone doesnt already know this...solar heating is by far the most cost effective way to go renewable. so it seems the cost to that part of the system is already low. seems like an easy marriage, what am i missing?
CinciTDI | TDIClub | My Desultory Blog
sorry Rich, but it seems that its now ur duty to do something. u got everything u need; desire and some brains with everything else easily gotten once those two tools are in place.
also, dont discount the pro's + gov subsidies. in my part of the world, after everything is said and done, ~5000$ gets u a done pro system that will do a considerable amount of heating.
flectere si nequeo superos, Achaeronta movebo! -Virgil
froggy: Mike Briggs:Simple old normal silicon panels can convert 45% of the energy in sunlight into free electron energy - the problem is that a lot of the electron/electron-hole pairs just fall right back into their non-excited states, and the additional heat energy from absorbing photons with greater than the bandgap energy goes into thermal energy of the electrons, making them harder to direct in the direction you want them to go to create a usable current. That's what brings the actual efficiencies down to 10-20%, while the actual sunlight harvesting efficiency is generally around 45% (note that that is essentially the same as the sunlight harvesting efficiency of photosynthesis. PVs can use a greater portion of the spectrum, but the energy above the bandgap energy just goes into waste heat (which further reduces the efficiency by increasing the electron thermal energy). PV's can only use 45% of the sunlight spectrum here on earth, but they absorb photons based on resonant wavelength excitation, so the full photon energy is harvested. so if the above is true, then why doesnt someone figure out a way to co-generate heat & electricity? maybe by somehow injecting water/coolent into the system as a heat sink with some sort of rankine cycle.
Mike Briggs:Simple old normal silicon panels can convert 45% of the energy in sunlight into free electron energy - the problem is that a lot of the electron/electron-hole pairs just fall right back into their non-excited states, and the additional heat energy from absorbing photons with greater than the bandgap energy goes into thermal energy of the electrons, making them harder to direct in the direction you want them to go to create a usable current. That's what brings the actual efficiencies down to 10-20%, while the actual sunlight harvesting efficiency is generally around 45% (note that that is essentially the same as the sunlight harvesting efficiency of photosynthesis. PVs can use a greater portion of the spectrum, but the energy above the bandgap energy just goes into waste heat (which further reduces the efficiency by increasing the electron thermal energy). PV's can only use 45% of the sunlight spectrum here on earth, but they absorb photons based on resonant wavelength excitation, so the full photon energy is harvested.
so if the above is true, then why doesnt someone figure out a way to co-generate heat & electricity? maybe by somehow injecting water/coolent into the system as a heat sink with some sort of rankine cycle.
Or using reverse peltier devices to turn that heat into electricity. I'm not sure why nobody is taking that approach (I've wondered the same thing) - instead everyone working on PVs seems to just take the view "heat bad, must eliminate" - without trying to do anything useful with it.
Generally when you have excess heat on your PV to the point of hurting efficiency, the ambient temperature is fairly warm, so you wouldn't have any need for solar heating (at least not space heating - heating water is always an option). That said, running tap water across a radiator for pulling heat off of PVs while pre-heating water for a solar hot water system IMO is an appealing option. I do find the option of integrating reverse Peltier devices into PVs worth pursuing though.
Solar thermal electric systems are likely to always be a more economical means of producing electricity from sunlight - but generally such systems are more appropriate for large, commercial power plant scales, rather than homesized systems (although dish style systems that focus concentrated sunlight on a Sterling Engine could have the potential to enter the home-scale market. I've wanted to try building one for a little while. Too much on my plate though already. I've been hoping to get one built as a "demonstration" item to go in our new physics building, when it's built (old building to be torn down in June (hopefully after we've moved out , new one to be completed about 15 months afterwards)).
BTW, the issue I mentioned above about excess energy above the band-gap energy in a PV semiconductor being wasted (and worse, reducing overall PV efficiency by increasing electron thermal energy, so the electric field at the N-P junction (which is what effectively creates a usable current from the electrons excited by photons hitting the semiconductor, by directing them in a particular direction) has less effect, being less able to direct them as desired), gets to the issue of why I don't feel you can say that PVs have to be more efficient than photosynthesis due to being able to use a larger portion of the spectrum. They can use a larger portion, but energy above the bandgap energy is wasted, and decreases system efficiency. Photosynthesis doesn't revolve around photon capture by exciting electrons over the bandgap, instead based on resonant energy capture - photons with energies that resonate with the free electrons traveling around the covalent path around the porphyrin ring of the pigments are absorbed, with their energy going to the electron. So, each pigment only has generally two resonant energies that they can capture - and they don't capture photons with energy above those energies (since their photon capture relies on resonance, not just bumping electrons into the conduction band). On the plus side though, photosynthesis uses multiple pigments with different resonant energies to create a resonant energy band that covers a substantial portion of the incident light spectrum (in terms of energy), and is somewhat more efficient as far as how much of the energy is captured from each photon absorbed, because of relying on resonance rather than bandgap jumping.
Rod W:Actually, solar panels at the current price point and efficiency are economically competitive, that's why we're having them installed on our new house. With a 25 year mortgage we'll be paying less than we currently do for rent and heating, and our running costs should be close to zero. Indeed, we may even turn a very small profit. So I can't grumble about the cost of solar.
What are you having installed, and what's the cost, if I may ask?
Rich: froggy: also, if everyone doesnt already know this...solar heating is by far the most cost effective way to go renewable. so it seems the cost to that part of the system is already low. seems like an easy marriage, what am i missing? I'm thinking about revisiting a project (see old post) that I never did get around to updating. I still use the hoses around the yard with the small 110v pump to heat water for the swimming pool. I've been contemplating a roof style collector for a few years but had trouble justifying the cost. I've collected a few 'discount bin' priced rolls of copper refrigerator tubing and was thinking about placing it in 'roof oven' ... Thoughts, cautions, best color, box design materials and pump/gravity system? (no hills around)
froggy: also, if everyone doesnt already know this...solar heating is by far the most cost effective way to go renewable. so it seems the cost to that part of the system is already low. seems like an easy marriage, what am i missing?
If you want to make your own solar hot water system, I'd highly recommend subscribing to Home Power magazine - there are often writeups in there by people who have built their own "gorilla" hot water system (and also writeups about installations using commercially produced panels, etc.). I'll probably do one this spring - but using commercially produced panels. You just can't get the efficiency with a home-built system - unless you have access to selective solar absorption coatings (molybdenum, etc.) and can make a nice low vacuum chamber that will hold vacuum for many years.
Mike Briggs: What are you having installed, and what's the cost, if I may ask?
We're having Sharp 3.67 kW photovoltaic panels installed on our south facing roof. They cost 2,260,000 yen with a 293,000 yen rebate from the city. We're also having an Eco-Cute heat pump installed which costs 639,000 yen with a rebate of 50,000 yen. Our energy usage is already paltry and with a better insulated house, it should be even less.
For reference 1 US Dollar = 118.362 Japanese Yen
How does that compare with a similar system in the US?
im a big fan of heat pumps/geo thermal on a distributive basis. i cant wait until we start piping the roads, roofs and other heat sinks. water is a very clean battery:)
Rod W: Mike Briggs: What are you having installed, and what's the cost, if I may ask? We're having Sharp 3.67 kW photovoltaic panels installed on our south facing roof. They cost 2,260,000 yen with a 293,000 yen rebate from the city.
We're having Sharp 3.67 kW photovoltaic panels installed on our south facing roof. They cost 2,260,000 yen with a 293,000 yen rebate from the city.
Yen? WTF? Oh, you're not in the US.
We're also having an Eco-Cute heat pump installed which costs 639,000 yen with a rebate of 50,000 yen. Our energy usage is already paltry and with a better insulated house, it should be even less. For reference 1 US Dollar = 118.362 Japanese Yen How does that compare with a similar system in the US?
Hm, so that's about $20,000 for a 3.67kW system.... I don't know what current costs are in the US, but when I was checking a few years ago, it was a bit more than that for that sized system (including installation - I get vertigo, so doing anything on the roof is a no-go for me).
froggy: i cant wait until we start piping the roads...
i cant wait until we start piping the roads...
At one time I was considering designing/building/owning a laundromat. Was seriously considering piping the macadam parking lot for summer water preheat.
Two '96 VW TDI B4 variants, '87 MB 300TD, '97 Ram 2500 Cummins, '89 Ford F250 diesel, Kubota lawn tractor, Diesel Generator... 31 Cylinders Kicking on the Sweet Sauce of the Soybean
http://www.renewableenergyaccess.com/rea/news/story;jsessionid=5C2F07A896239A5529C2D8B64E215DA0?id=47009
here is a mortgage company that is willing to take the risk...
it seems perfectly natural to have ur solar panel paid by the mortgage upfront.
Rich:This is interesting ... let us know how it goes Ron.
Well I contacted an "associate" about a month ago, registered at that time, E-mailed him a week ago to see what's up... and haven't heard hide nor hair from anybody. Kinda frustrating.
Hello gentlemen - I just came upon this thread and was disappointed to read that you had not received a satisfactory response to your queries. Furthermore, I must apologize for the unauthorized wording of the independently placed ad which first drew your attention. It misrepresents the company and its motives. While it is true that the solar panels in question do not need to be purchased, suggesting that they are 'FREE' is misleading and undignified. We have taken strict measures to ensure that this sort of thing does not recur.
Still suspicious of a scam? We understand. But if it were a scam, it's the worst one ever designed: No one is being asked for any money or other valuables up front. Not salespeople, not customers.
So, what is the real story behind the ads. Here is an overview of the forthcoming REnU rental service that will dramatically change the solar electricity equation and at last tip the balance towards solar photovoltaic generation in this country..
First a couple of references:
REnU website: JoinTheSolution.com. This home page also links at the upper right to an ECO-produced streaming video which also features Ed Begley, Jr.In 1994, Dr. Robert H. Wills, P.E ., Principal Electrical Engineer, Solar Design Associates, Inc., Architects and Engineers, Harvard, Massachusetts, published a paper entitled, "The Interconnection of Photovoltaic Power Systems with the Utility Grid: An Overview for Utility Engineers". It detailed the many changes necessary at that time for PV to overcome its historical failure to become widely adopted. The document is hosted at http://www.sandia.gov/pv/docs/DOC/Interconnect.doc
Now the good news:
Dr. Wills is now the company's Executive Vice-President and CTO. The obstacles have been overcome, opening the door to transforming the way solar PV generating capability is acquired. It will make Residential Solar Electricity easy to get, and affordable. It will make financial sense. It will be a very good thing.
And the slightly-not-as-good news:
It will not come about immediately. The first few trial installations in the country will occur sometime this summer. Manufacturing capacity will require a period of two years to reach 100%. But at approximately 20% of full production output circa September 2007, REnU systems will begin producing electricity from the sun in neighborhoods all over the United States.
You're allowed to be skeptical. We were. But you're going to be hearing a lot more about REnU. The company is poised to become the largest PV manufacturer in the world. Its objective is to significantly reshape the solar PV electricity market, and promote solar to a long-overdue position o