Dave Watts from Solera came over the day we were heading out of town for the Spring Break with our kids. He did a walk through and agreed to come back in a few weeks to assess the solar capacity of our house. It seems the huge Maple tree in our front yard would impede the feasability of using solar photovoltaic. He thought that solar thermal might still be a viable option for us, but he wanted to check with Zerofootprint about the viability of geothermal for our place

In the meantime, I looked up stats re energy efficiencies using renewables. Here's what I found out:

In addition to passive solar energy -- which makes best use of allowing natural sunlight to heat your house, or not, depending on the season and the time of day -- we need to look at Solar Thermal and Solar Photovoltaic.

Solar Domestic Hot Water Systems (SDH)

The SDHW system connects to a home's existing gas or electric water heating system, providing a supplemental source of heat for all hot water needs including showers, dishwashing, clothes washing,and cooking. Solar water heating systems are a proven technology that work well even in cold climates.

One of the most common questions on SDHW is whether or not Canada has enough sunlight to support solar applications such as water heating. Natural Resources Canada reports that there is enough solar energy to deliver an average of 2500 kWh of energy per year. This means that solar energy can provide enough hot water for approximately half of the hot water needs of a family of four.

A year-round solar water heater system will provide 35 to 55% of annual water heating needs. In summer, it will provide 75 to 100% of hot water and in winter it will provide 10 to 25%. At 2001 energy prices, in most Canadian homes, that is a savings of $150 to $500 per year. A system would be expected to pay for itself in 8 to 12 years, although the actual payback period depends on system size and future energy prices. However, the larger a consumer of hot water you are the more you stand to gain financially from a solar thermal water heating system.(Source: http://www.cansia.ca/downloads/factsheets/23.pdf

Question #1: Given that we're not large consumers of domestic hot water, I wondered if this would be the best use of our investment into solar energy?

Solar Home Heating

Question #2: Given our high-efficiency boiler which we installed in 2002, would using solar with a heat exchanger to heat the house be the best use of our financial contribution/investment into renewable energy?

A typical 4-panel residential system that provides both heat and hot water will cost about US$11,000 - $12,000 after state and federal incentives.
Source: http://www.solarserviceinc.com/faq.html#6)

Dave from Solera said the thermal system could be used for both home heating and domestic hot water heating. This sounds like a more cost effective choice. He told us that our relatively new boiler (Weil-McLain Gold CGI-3 Series 2 AFUE 84.3%) enables easy connection from other sources, and it would be a snap to install a solar thermal system that would supplement our home heating.

So we should look at a solar thermal solution to couple with our high efficiency boiler, which is known as a solar combisystem.

Solar Combisystem

Solar combisystems generally consist of five elements: a solar collector loop; a storage subsystem; a control subsystem; an auxiliary subsystem; and a heat distribution subsystem. Solar combisystems do not generally refer to systems with cooling capabilities. In special designs, the storage subsystem can be combined with the heat distribution subsystem, e. g. floor heating.

I sourced one Ontario built combisystem through Enerworks, but the Toronto rep said we must have 2 systems to supply DHW and home heating.  But, apprently this isn't the case. You can get combo tanks that effectively separate the solar pre-heated water. So we'll need to investigate.

Question #3: How much electricity is needed to run a comibsystem?

How the solar water heating system is pumped and controlled determines whether it is a zero carbon or a low carbon system. Low carbon systems principally use electricity to circulate the fluid through the collector. The use of electricity typically reduces the carbon savings of a system by 10% to 20%.

It is important to remember, however, that the main need for central heating is at night when there is no sunlight and in winter when solar gain is lower. Therefore solar water heating for washing and bathing is often a better application than central heating because supply and demand are better matched.

SOLAR PHOTOVOLTAIC

Here's some info re costs of photovoltaic, but given the shortage of silicon (read recent article in Wired)  solar technology may not get that much cheaper. I found out from the Enerworks rep that China is producing some really cheap collectors, some of which are breaking down after 3 years instead of having a shelf-file of 25-30 years expected from good quality collectors.

In 2003, a residential solar system cost about $8,000-$12,000 per kWp installed. A 1kWp System will produce approximately 1250 kWh/year in Toronto.