Solar Power for Existing Homes
Before seriously considering installing any type of solar system you should first
evaluated your home searching for any areas that could be made more efficient. While solar can heat a leaky old un-insulated farmhouse it would take hundreds of tubes and the cost would be prohibitive. Generally the common upgrades in insulation and weatherization will pay for themselves much faster than a solar system. The less fuel or electricity you need, the smaller, and less expensive your solar system will be. Remember most solar systems are expandable, especially if you plan for it when the system is designed.
We can now provide full energy audits, with BPI certified auditors. The Maine Home Performance program provides financial incentives to get your home weatherized and to install solar hot water.
The list of “solar systems” include; Solar Thermal for heat and hot water, PV-Photovoltaic, or wind, for electricity. GeoThermal and heat pumps for heating and cooling, or a solar hot air sheet for supplementing space heat. While all these applications are not strictly “solar” they all rely on mother nature.
The 2 panels on the right are solar thermal, all the remaining panels are PV electric. This is a common ratio.
Generally Solar Thermal Hot water systems will pay back their initial investment the quickest, usually 5-6 years after incentives at a cost before incentives of $8,000-$12,000. PV is closer to 10 years for most homes at a cost over $30,000. If you have a suitable site for wind, normally it costs less than PV. Geo-thermal heat pumps are generally not practical on a retro-fit of an existing home because of the disruption to the lot. New air heat pumps provide a cost effective solution for most of they year, combining heating with cooling ability. Our concern with heat pumps relates to future cost of operation as electricity rates rise.
System Design Considerations
Often solar thermal or PV panels are mounted on the roof. We will need to decide where to route the plumbing and electrical lines to reach your hot water storage 
tank or electrical service panel. If no suitable interior chase way can be found, we can run them outside enclosed in a product called slim-duct (see photo, right), that looks much like a gutter downspout. Lines can be insulated and buried.
Solar systems can easily grow with your family or home provided you plan ahead and properly size the piping.
Locating your solar system collector panels
Collectors are generally roof mounted, but can be ground mounted on a rack, or placed on a secondary building. Generally collectors like to face south. Solar thermal is more forgiving and can face east/west. Collectors need to be in the sun and not shaded by rooflines. With a tool called a Path Finder we can check for seasonal shading that may be caused by nearby trees or buildings. Sometimes some summer shading from a tree on a solar thermal panel can actually be beneficial to reduce excess summer output.
We have seen beautiful cedar pergolas, window overhangs that also provide summer shading, and railings all done with solar thermal evacuated tubes. In these cases they look like architectural elements, not solar tubes. Velux makes a great solar thermal flat panel collector. While it does not have the winter output to provide space heating, for domestic hot water it is a great choice if you object to the look of other collectors. Velux’s product integrates with their skylights, having the same size and reveals. They are flashed into the roof for a very streamline look. Winter output is best when they face true south on a highly pitched roof.
4 Velux solar thermal panels with a skylight at each end.
Photovoltaic (PV) electric systems manufactures are coming out with exciting options. Thin film seems to be they upcoming technology. Right now it is practical for metal roof installations. The thin film is glued to the roof for a visually pleasing look. There are new mesh type PV fabrics that can be shade structures as well as power generators. During 2009 increased competition and global oversupply dropped the cost of standard PV panels significantly. If you have a building site where bringing in power lines is cost prohibitive, an off-grid battery bank system may be the answer. Most homeowners elect to be grid tied to avoid the cost and maintenance associated with batteries. In these cases you pull your power from the grid. You are credited for power created and debited for what you use over a 12 month window. If you have concerns about loosing grid power, you can add a small battery bank to come on in case of a power outage.
We can provide all the plumbing, radiant and heating products and installation in addition to installing your solar system, or we can work with your builder or plumber. Installing a standard solar thermal hot water system normally takes only a few days.
Solar thermal systems
- You will need a large storage tank, plan on 20-40 gallons per person, more if you are doing space heating.
- If you are going to heat your pool or hot tub, you need to decide where you would like the plumbing lines routed. They may be insulated and buried.
- If you purchase a data logger and want to routinely check it, have it installed in a convenient location. It is possible to place monitoring equipment anywhere so you do not have to go to the basement to check system performance.
Consider Marathon hot water tanks to store your hot water we use high efficiency tanks. Marathon’s warranty insures it is the last tank you will ever need to buy for your home and its heat loss is only 5° per day. It is a great hot water tank, as well as solar storage tank.
PV – Photovoltaic systems
- A rough estimate is 100sqft of collector generates 1kwh. PV panels like to be within 10° of south.
- A PV system does not need to meet 100% of your needs if you remain grid tied. Additional power will be drawn from the grid as necessary. You are credited for electricity created, and debited for use, over a 12 month window. If you are concerned about power outages a small battery bank can be tied into the system.
- If you are off grid a battery bank and some sort of backup system needs to be in place. Batteries need water, and a separate storage area away from any living space is best. You will need lighting in the area to regularly check the batteries.
- If you install data loggers, and want to routinely check performance make sure they are located in a convenient location.
Wind systems
Many people are fond of the idea and look of a windmill. Often you will find a neighbor that does not want your wind turbine to block their view. Some cities have codes against wind turbines, usually restricting height to lot size. Often there are fewer objections to the Tangarie vertical wind turbines we sell since they are smaller, quiet, do not strobe or harm birds. To successfully run a wind turbine you need an appropriate site. If you are not 100% sure of the wind speeds have a wind study done. We have seen many windmills place in unsuitable locations, between buildings, blocked by trees, not generating the output expected.