BuildingGreen, the publisher of the GreenSpec Directory, which contains 2,000 environmentally preferable products, has announced their list of Top-10 Green Building Products for 2008.

First, let me say of Photovoltaic Systems that SustainaBuild would recommend that you "first reduce (your energy consumption), then produce". This is true both in terms of cost-effectiveness of increasing your home's energy efficiency and in cost-effectiveness of reducing greenhouse emissions. For most budgets and most homes, there are a number of things that should be done to improve a home's energy efficiency before it would make sense to install Photovoltaic systems, especially in the sun-deprived portions of the PNW. However, the appeal of having free power cannot be denied so let's take a look at where PV currently stands.

The Basics

PV technology converts sunlight directly into electricity. PV modules are measured in terms of Watt-Peaks- the output of electricity under standardized conditions. Although different modules will perform differently under the same conditions, watt-peaks is still a fairly good measure of how powerful a module can be. So, if we have a system with watt-peaks of 3kw, and assuming constant sunlight of 24 hours per day, this would produce about 72kwh per day. We obviously don't have 24 hours of constant sunlight in the Northwest. So how do we know how many hours of sunlight we can expect per day? Insolation. Insolation tells us the amount of solar radiation received at any given area and time. More simply, this can be expressed as sun hours/day. For Seattle/Tacoma, our average is 3.57 sun hours per day, compared to 6.58 for Phoenix. So, in our region, with a 3kw system and about 3.5 hours of sun/day, we can expect to produce on average, 10.71 kwh/day.Given, the fact that the avaerage family uses about 30kwh/day, the current power rates of 8.5 cents/ kwh, and that the cost of a PV system this size would be around $24,000, the payback on this would be well over 30 years. That isn't great right now but things will change.

NanoSolar

Currently, crystalline silicon modules retail for around $8/watt. This is expected to decrease as demand of PV and as the price of electricity goes up. Nanosolar is perhaps the most promosing of low-cost PV systems.

Nanosolar was founded in 2002 with the stated goal of selling PV cells for $1/watt. They are able to produce their panels more cheaply as they simply print the semiconductor of a high-performance solar cell, while only being slightly less efficient than standard PV modules. Nanosolar made its first shipment at the end of 2007. They are currently sold out for the next year, and they are currently not selling to small scale or residential customers. It also isn't clear if they are selling for $1/ watt, although they have not indicated otherwise. When and if they do become available for smaller projects at a $2/ watt installed price, this would give us a much more desirable payback period of around 15 years in the above example. While some companies are focusing on reducing the cost of PV, others are attempting to increase the efficiencies of the panels up to around 50%, which would also help make PV much more feasible. While it remains to be seen when and how low prices will fall, it is very certain that they will go down.

Incentives

Tucked into the recent $700 Billion Bailout were some provisions towards making PV more affordable, including an extension of the 30% tax credit for PV installations, and more importantly the removal of the $2,000 cap on this credit. Also getting in on the incentive action is the State of Washington that will pay homeowners 15 cents/Kwh for energy that is supplied back to the grid, or 54 cents/Kwh if the equipment is manufactured in WA (although I don't believe there currently are any Washington manufacturers). This incentive is currently capped at $2,000.

Where PV Stands

If you have done everything you can to reduce your energy consumption and have room in your budget to add solar energy, then PV might be the right choice. For the rest of us with a limited budget, PV systems may have to wait until they are more feasible. SustainaBuild recommends that if you are going to be making changes to your home, to consider pre-wiring for PV so that when PV becomes more feasible you will be ready to add PV technology without significant changes to your infrastructure. As far as the most cost-effective way of capturing solar energy in the Northwest, consider Evacuated Tube Systems, which pre-heat water effectively, even in sun-challenged locations.

Popoular Mechanics Debunks 5 Recycling Half-Truths

In Western Washington, the two most common choices for fuel type are electricity and natural gas. While some factors affecting which one to choose are relatively straight forward and obvious- cost, availability, compatibility with heating system, efficiency- one factor requires some number crunching and investigation- the effects of the fuel type on the environment. For many, the other factors may preclude which fuel type is eventually chosen. However, it is important to understand the impacts of the fuel choice on the environment.

The largest single effect of the fuel choice on the environment is the amount of greenhouses gases- most notably, carbon dioxide and methane- that are released into the environment for every unit of energy used. Natural Gas is mined, processed, and delivered to your house without emitting any greenhouse gases. Only after combustion in a furnace, stove, or water heater does it release Carbon Dioxide, and this amount is minimal when compared to electricity.

In order to produce and deliver electricy, significant greenhouse gases are released before the energy arrives at your home. This is because electricity is a secondary energy. It is produced by converting other forms of energy into electricity: hydroelectric, coal, natural gas, oil, nuclear. With Puget Sound Energy, 37% of its electricity is derived from coal, while 19% comes from natural gas. The process to convert these fossil fuel feedstocks into electricity is very inefficient. A fossil fueled electric plant converts only about 33% of its original feedstock into electricity as 67% of it is wasted in the process. Another 9% is lost as it travels through power lines to your home. Considering about half of all PSE electricity is derived from fossil fuel origins, this means that it takes about 80% more fossil fuels to produce , deliver, and use a unit of electricity as it does to produce , deliver, and use the equivalent of natural gas. This also means that electricity production releases more greenhouse gases than does Natural Gas combustion. According to the EPA, 0.90 lbs of Carbon Dioxide are emmitted for every kWh of electricity when using PSE, compared to .39 lbs for natural gas. All of this would suggest that natural gas is more beneficial from an emissions standpoint.

But like most issues in green building, the issue of gas vs. electricity is not cut-and-dry and other facts must be accounted for and then weighed against each other. Here are a few:



1.) What is your utility's fuel mix?
Compared to other states, Washington utilities rank 47th in the amount of fossil fuels used to produce electricity, as we rely mostly on hydroelectric power. Other states rely more on coal, making natural gas that much more attractive.

2.) What appliances will the fuel feed?
The more efficient the appliance is at using electricity vs. natural gas, the less attractive gas becomes from an environmental standpoint. For example, a mini-split heat pump produces four to six times more heat than the electricity it consumes. If you compare this to a natural gas furnace that converts 90% of the incoming energy into heat, then the electric air heat pump is more attractive, from both an emissions and a cost of energy standpoint.

3.) Does your utility offer green power?
PSE currently offers the option to buy green power from renewable sources (wind, solar, biomass, geothermal) at a rate of $0.0125 per kWh, potentially negating the greenhouse gas aspect of electricity production.

4.) Cost.
Currently, with PSE, the price of natural gas is about 45% less than the cost of electricity, making natural gas even more desirable. However, this is expected to rise and eventually surpass the price of electricity.