Just bought a house and have some questions.

System · January 2008

Hi. I'm new. My name is Aaron and I live in central Wisconsin and I'm interested in solar power.

I have a big 6-12 pitch roof with lots of surface area pointing due south. It gets all day sun this time of year so I'm sure summer will be even better. I'm going to be putting in a new furnace system this next year and I'm seeing how fossil fuels are getting insanely expensive. I have an idea that I wanted to run past you guys. I wonder if I put in an electric boiler and baseboards if I could significantly offset the cost of heating with electric with solar panels when you consider generating power over the whole year? I see there's a ton or rebates and grants here for solar and windmills. I'm in town and I'm on the grid.

What other equipment would I need other than the pannels?

mike95490 · January 2008

Re: Just bought a house and have some questions.

I'd do 2 things.

1) look into solar water heating via "Evacuated Tube" collectors. Heating water directly is a whole lot more efficient than collecting solar electric, and using that for heat.

2) after your solar hot water is in, then consider solar electric in a Grid-Tie configuration to trim your electric bill.

Mike

icarus · January 2008

Re: Just bought a house and have some questions.

Using resistance electric heating of any kind is VERY expensive to do using Photo electric solar. As Mike has suggested, use direct solar for water/space heat, and PV for other electrical needs.

For example a 2.5kw electric baseboard would need 2.5kw of panel just to power the one baseboard, coming at an up front cost of $10-20,000.

The basic rule for any RE system (should be for all energy systems!) is use efficiency first, efficiency second and efficiency third. After that, look into Solarizing your home.

icarus

Solar Guppy · January 2008

Re: Just bought a house and have some questions.

PV and resistance heating is DOA

do some google searchs for Solar Thermal ... both air and water based.

With direct southeren exposure the home would do well with something as simple as large windows, there are alot of good books on homes built to use solar thermal ... thats the path to be thinking about for your home.

Brock · January 2008

Re: Just bought a house and have some questions.

What they all said, solar hot water is the way to go and it works up here. My brother just finished his solar hot water install and heats his hew house with hot water, radiant tubing in the basement cement floor as well as under the main floor. I have geothermal and solar PV in the house we are building now. My brother is in Denmark and I am in Green Bay. Hey if you haven't gone to the Midwest renewal energy fair it is a must and it's in our own backyard, over near Custer or Stevens Point every summer. http://www.the-mrea.org/energy_fair.php

dale · January 2008

Re: Just bought a house and have some questions.

I've got an oil boiler. I've heard people discussing using a direct solar water heating to pre-heat the water going into the boiler.

If, for example, the boiler hot water settings are 140-200 degree and the solar could preheat to 120 degrees, then it could reduce the work load on the boiler. Has anyone heard of anyone using direct solar heat for this purpose? Then, would it be worth the cost?

BB. · January 2008

Re: Just bought a house and have some questions.

Dale, have you looked at all of the efficiency gains that can be made?

You are, I assume, in a colder climate than I (near SF, CA), so my 70 year old home originally came with zero insulation and a big gas heater to keep it warm. And that your home probably has more insulation than mine did (or probably even now--given that I only have 2x4 walls).

I replaced the windows (double pane vinyl), stripped walls to add insulation, added operating skylights for summer ventilation and natural lighting to dark hallways/rooms, CFLs, replaced old gas furnace insulated and sealed heating ducts, installed Energy Star appliances, on everyone to turn off lights, etc... before I installed my Grid Tied Solar Electric system...

Also, I don't know the details of oil fired furnaces and how your installation works--but 200F sounds awfully hot for baseboard/domestic hot water. Generally, the lower you can heat the water, the more efficient the system can be. Of course, there are downsides, larger radiator surfaces, possible rusting of your oil burning furnace (from condensation), etc...

Adding a solar hot water system as a boost to an existing heating plant can introduce other problems (problems with freezing, overheating feed water, electronics/controllers to manage system, additional pumps, back flow, pressures, system chemicals, electrolysis between the different metals, etc.)--so if you want to do this, you probably need to take your furnace guy out for a beer and discuss the details and issues.

It might be easier (and cheaper) to do a solar hot water system independent of your existing oil heating system. I.e., installing a domestic solar hot water system for showers/washing and just plumb in your oil system as a backup heat source (such as a circulation loop in your solar hot water storage tank). See how that works, then plan on enlarging or creating a second RE system for home heating.

My two cents worth...

-Bill

icarus · January 2008

Re: Just bought a house and have some questions.

People do it all the time. Heat is heat, whether it goes into domestic hot water or domestic heat. Look into evacuated tube type systems as they are very efficient and post little problem with freezing.

Icarus

PS. As Bill suggests, look to efficiency of the building first, second and third, before you spring for expensive RE systems. Most up front costs of adding efficiency will pay off way faster than RE, and then the cost of any RE system would be by nature smaller and therefore cheaper.

Good luck,

Icarus

Brock · January 2008

Re: Just bought a house and have some questions.

Dale that is what my brother does. His 80 gallon propane fired hot water heater has a coil in it that is heated by the solar hot water system, and the solar heater is set for 140F, his propane is set to come on at 120F. He uses this same tank for domestic hot water as well as radiant in floor heating through yet another exchanger. So far it has worked for him. He added the solar hot water this year and said it has about cut is propane use in half since he installed them. He only has two 4x8 panels, which seemed small to me, but in summer they were worried about having to much heat? I don't understand solar hot water that well yet.

Just bought a house and have some questions.

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