Best Solar System To Power A Home

by Steve
(Montreal, Canada)

QUESTION:
I have a suburban home that gets plenty of sun in the afternoon, but is shaded during the morning. What is the best way to reduce my energy bill? Should I use active solar panels or passive thermal heating.
ANSWER:

Steve, thanks for your question. Yours is an interesting case as there are quite a few factors to be taken into account in working out the best solution. However, the short answer to your question is that we believe you would be best served by investing in thermal passive heating for your home.

And here's why...

Your Energy Needs


The starting point in any solar energy project is to work out exactly what it is that you are trying to achieve.

The first step is to do an assessment of your energy usage. In order to do that you need to look in some detail at all the appliances you use in your home. To help you do that we have summarized data from the US Department of Energy and you can download it by clicking here. You can use that to determine the cost of operating each appliance, using the utility company rate for your electricity.

Energy savings within your current situation are always a good first step. A dollar saved with energy efficiencies saves you more dollars on any new system.

You can easily calculate your annual electricity usage from your utility company bills. If you want to reduce that or remove it entirely then you need to work out your system size accordingly.

Once you have made that decision then you can look at the best way to go about it.

Let's start by looking at setting up a solar panel system to generate electricity for your home.

Location


Solar PV panels really need maximum exposure to the sun. The term often used is "peak sun" and this is defined as being exposed to the sun between 9.00am and 3.00pm.

Since you live in Montreal Canada, the insolation factor is an important consideration. Insolation is usually defined as the amount of solar radiation reaching a particular area at times of peak sun, usually expressed as watts or kilowatts/sq. meter/day. In Montreal, on average, that is 3.37 KW-hrs/sq. meter/day. It ranges from a low of 1.22 in December to a high of 5.43 in June, according to data from NASA.

In order for any solar panel to perform at its best you need to locate it where it receives peak sun and this is achieved by facing it true South and tilting it at the latitude in which Montreal lies, about 45°. The usual position is on the roof of your home but it is also possible to have it ground mounted.

You describe your home as being shaded in the morning but with sun in the afternoon. You don't give any information about roof orientation or the presence of topographical features that contribute to this shading effect. However, it is safe to say that a rooftop solar panel would not get peak sun and therefore produce less electricity than you could otherwise expect.

The only way to get peak performance from your panel would be to locate it at ground level to get a south orientation. This would depend on whether your property would lend itself to that configuration.

It is important to note that if any portion of your solar panel is shaded then performance will suffer considerably. Even the shading of just one cell in your panel can cause a big drop in production. It can also damage the cells concerned.

Manufacturers of panels address this issue by including bypass diodes that prevent damage to the cells and lessen the shading effect. However, full power is still not attained. In other words, panels with bypass diodes are less efficient.

Return On Investment


Solar panel systems are not cheap. The costs are coming down with technology improvements but even so you are facing a substantial outlay. To give you just a ball park figure – if you wanted to buy a system that generates 6,000 Kw-hrs per year then you will probably outlay $12,000, not including installation.

Therefore you need to be able to get some incentives or assistance to realize a good return on your investment. However, our investigations indicate that the Government of Canada via its ecoENERGY Retrofit program has grants available but that the program expires in June 2012. Perhaps it will be renewed or extended.

Quebec province has no incentive programs for solar energy projects and nor does it provide for feed-in tariffs, unlike Ontario province which seems to be leading the way in this regard in Canada.

Given that situation and your location issues it seems as though a solar electricity program is not particularly attractive at present.

So let's look at the alternative of using passive thermal heating.

In the great majority of households the greatest energy consumption is in the areas of space heating, hot water production and cooling. It is in these areas that solar thermal systems excel.

Collecting The Heat


There are three established ways of passive heat collection, known as direct gain, indirect gain and isolated gain.

Let's look at each of these in more detail.

Direct gain passive thermal heating


In this system the sunlight enters through south facing windows insulated with transparent glazing. The building warms up because the heat is retained. In the evening the heat is distributed via convection.

Indirect gain passive thermal heating


The difference here is that the thermal mass is placed between the sun and your home. The most commonly used methods are Trombe walls and water walls.. In all these cases the heat is collected and then transferred to the house interior by a variety of means including vents, ducts, doors & natural convection.

Isolated gain


This method involves collecting the solar heat in one area and transferring it to a different area, in this case, your house. An example of this is a sun-room which can be attached to or separate from the house. It needs to be well insulated so as to retain the heat gathered during the day and that heat is then transferred to the house by whatever means are best suited to the situation.

Passive solar heating is definitely better for your budget as it costs less to set up than a solar electric system.

Without knowing the layout, configuration and construction materials of your house it is difficult to be more specific on the type of passive solar system that will fit best.

However, we recommend visiting the following site:

http://www.radiantsolar.com/index.php

This is an excellent site with great information and also because they provide packages that are set up for doing-it-yourself. They offer free advice and quotes and telephone support. Definitely worth a look.

Steve, I hope this has given you some information to work with and that you are able to switch to solar with good results.

Ian Purdie
BlueRam Group

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