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Author Topic: Photvoltaics (PV)  (Read 7942 times)

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    • Renwable Revolution
Re: Photvoltaics (PV)
« Reply #285 on: June 16, 2018, 10:37:39 pm »
From my inputs, they claim I would need 67 X 360W PANELS :o plus a 13.5KW battery. Besides the fact that I could only get about a third of that many panels on the south side of my roof, it's just too much money.  :(

The way I would recommend using solar in your unique situation ( should you ever wish to) is to build a very simple parallel system with one large panel (scaling up eventually to perhaps two panels)  and a small battery array, and run SOMETHING off it. A dedicated circuit for your refrigerator, perhaps. If that's too big a load you could run lights.

An MPPT charge controller helps with the shade problem.

I think it makes really better sense here of course. We have 5 hour sun. I could run my energy-sink McMansion with pool from a good rooftop grid-tie, and it would make my house more desirable to sell when I finally do downsize. I just hesitate to take on debt for that. But it would be required, because TPTB requires the job be done by pros, which implies it gets done fast and you have to pay for it all at once.

Agreed. The idea of a dedicated circuit has always appealed to me, particularly one where voltage regulation is not a big issue. For example, in the winter, though the total hours of sunlight are reduced, we actually get more direct sunlight on my home. Solar Panels (about 6KW) on the roof could easily be rigged for a dedicated heating circuit. Filament heating circuits, as long as you protect them from too much amperage (easy to do with solar Panels  ;)), could care less about voltage variation. All my heating is electric. I stopped using the kerosene fired furnace over 15 years ago. I have saved a lot of money by doing that and, since Green Mountain Power has a very large Renewable Energy portfolio, it has definitely lowered my carbon footprint.

Yes, the the fossil fuelers will be quick to blah, blah, blah about "kerosene/oil/fossil fuels are more efficient than electrical resistance for heating", but they are WRONG.

WHY? Because, though they are technically thermodynamically right when the two energy transfer systems are viewed in isolation, they FAIL TO add in the fuel cost of those trucks that carry that kerosene, their maintenance, AND the trucks that carry the kerosene from the refinery (and so on). No sir, they have this STRANGE idea that "energy going through wires costs the same to transport to your home" as energy going from an oil well to the refinery to the truck to the distributor to your home furnace to be burned. BULLSHIT.

Pardon my rant. ;D I also have issues with all this government permitting baloney TPTB place on us before we are allowed to get a Renewable Energy system going. More people are killed each year from misusing kerosene portable heaters than PV or wind electrical systems injuries by a factor easily of a thousand! But, no sir, we don't want to "overregulate" anything that uses fossil fuels, now do we? 😈

Well, at least the electricians are happy.  ::)
Actually I would not fault your logic or your right to choose but it really does depend on how your utility generates power. If your utility is well diversified with lots of hydro, wind some nukes and just a smidgen of natural gas electric heat will produce much less greenhouse gas. HOWEVER if your utility is reliant on natural gas and coal the numbers work against you. Central power plants turn fossil fuels into electricity at pretty horrible efficiency then you add line losses to it. My rule of thumb reference for that is this site here:  http://michaelbluejay.com/electricity/fuel.html
from that site the efficiency is:
Coal:  33.6%
Petroleum:  25.5-33.3%
Natural Gas:  29.4-44.8%
If you use natural gas as the best option and the most modern plant you get 44.8percent he uses 7.2 percent for line loss so 44.8x.928= 41.6 percent of its energy is turned into electricity the rest is vented as heat at the plant or lost to the air en route to you. A modern furnace is 80-90 percent efficient so yes if your utility uses fossil fuels to generate electricity you are better off using said fuels to heat your home directly if you are using baseboard heaters. Of course you will not do this SOOOOO if you want to totally destroy the fossil fuel math then the technology to invest in is the new generation of air to air heat pumps. Even on the coldest days you will be using 33 percent the electricity you currently are with your baseboards. They work down to about -25 celsius then their efficiency plummets down to that of baseboard heaters. You could if you invest in solar and air to air heat pumps make a net metered system work for you... Some states offer incentives as well. I really like the dedicated solar arrangement for building solar capacity. That is exactly how my house works. I replaced the backup generator with a grid connection and power some loads on solar some on grid. Right now I'm about evenly split. I will be installing a much more powerful modern array this year sometime. At that point I expect my utility portion to drop to almost nothing. I will keep it though its the cheapest backup generator you can buy.

Excellent post. I agree that air to air heat pumps are the BEST. The problem for me is that they are very expensive. Mitsubishi has a split something or other system that a Vermonter uses to heat his home extremely efficently. It's just not something I can afford. Also, they need to be inspected by qualified personnnel annually. All that costs money. One of my initial reasons for getting rid of the kerosene fired furnace was the maintenance people's habit of charging an arm and a leg for the annual inspection. And, if the electrodes needed changing or adjusting in the middle of the winter (No heat!), they charged $90 JUST TO COME TO MY HOME before the cost of parts and labor. For you, a skilled craftsman, those are not issues. For people like me, they are more costs that just keep adding up.

None of those costs exist when all you are doing is running electricity through a resistance to get heat.

I understand the inefficencies of the grid, particularly that part of the grid that gets its energy from burning fossil fuels. It's insanely inefficient, as you pointed out. GMP gets a huge part of its juice from wind and hydro, with a smaller part from solar and some "Renewable Energy credits" program, so my source is not that inefficient. Amory Lovins of the Rocky Mountain Institute has written and made several videos about that issue and other inefficencies in our civilization like the woefully inefficent pipe designs for all sorts of machinery, not just engines. Actually, the numbers you posted from that link are more friendly than what Amory Lovins has computed for those fossil fuels. Too often, the basic enthalpy of a hydrocarbon is what guides efficiency calculations. Amory Lovins adds all the other, often hidden, inefficiencies to those. But, I will not split hairs with you on that.

Here's a screenshot from one of the videos by Amory Lovins on the inefficiencies of our civilization:

Ideally, we would all heat and cool our houses with some kind of heat pump using either a geothermal source  getting piped air or some heat exchanger liquid from 30 feet or so below the ground, depending on where you live, or just going the air to air heat pump route with a Mitsubishi unit.

This is part of the Mitsubishi pitch:


Conventional heat pump systems are known for poor efficiency and performance in cold temperatures. Today, thanks to the integration of INVERTER-driven variable speed compressor technology, highly-efficient, modern heat pump systems offer homes optimized comfort conditioning no matter the season or temperature.


When utilizing a zoned HVAC configuration, each heat pump system consists of one or multiple ducted or ductless air handlers and an outdoor condensing unit. One outdoor unit can control up to eight indoor units, providing personalized temperature control, in each individual space, depending on the occupant's preference. Refrigerant lines connect the indoor unit to the outdoor unit. During summer, the system produces air conditioning when refrigerant absorbs heat energy from inside your home and expels it outdoors. During winter, the heat transfer process reverses as refrigerant extracts heat energy from the outside air and transfers the heat inside to warm your home. With the outdoor unit operating with INVERTER-driven compressor technology, the system speeds up or slows down to match the precise cooling and heating requirements of the space, keeping efficiencies high and costs down.


But beggars like me cannot be choosers. When Green Mountain Power (GMP) reaches 100% Renewable Energy, the only carbon dioxide I will be putting out, provided I buy and Electric Vehicle, is the CO2 I exhale. That is my goal, even if it isn't as efficient as using natural gas.
This poor man cried, and the Lord heard him, and saved him out of all his troubles.. -- Psalm 34:6


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