How It Works

There are two basic types of solar systems: photovoltaic and solar thermal. Photovoltaic systems produce electricity from sunlight while solar thermal systems are used to heat water for the building, saving on heating costs.

Of course, photovoltaic systems are most often cited when talking about solar energy, but many in the Northwest find that solar thermal systems are more economical to purchase and install and have a faster return on investment.

The most basic way to gauge which system is right for you is to consider your utility bills. If you use electricity for most of your home's energy usage, then photovoltaics are for you. If you use gas (propane or natural gas) for most of your energy, then you will likely benefit more from a solar thermal system.

Before you make up your mind, however, give us a call. Here at Solar Powered Solutions, LLC, we are experts in all things solar. We can sit down and crunch the numbers with you to show you how you can best be served and where you'll get the most benefit from a solar installation.

Read more about photovoltaic systems or solar thermal systems by clicking here.



How Solar Power Systems (Photovoltaics) Work

Photovoltaic panels (often called just "solar panels") generate electricity by reacting to specific wavelengths of light from the sun. This light hits the individual cells of the panel, react with the silicon there, and release electrons. Those electrons are then captured and moved through the cells and panel to the power system of the structure the panels help produce electricity for.

Most solar panels have three ratings associated with them. They are rated by their power capacity (number of watts produced), their efficiency over 24 hours, and their expected lifespan under normal conditions.

Power Capacity
The power capacity is measured in watts (usually kilowatts or kW). This will be listed as the maximum possible output the panel can produce in a given time frame. So a panel with a rating of 1.0kW/h can produce a maximum of 1 kilowatt per hour of full sunlight.

Efficiency Rating
The efficiency rating is usually expressed as a percentage of maximum to be expected in a given time frame when the panel is in optimal conditions. A photovoltaic panel will be positioned at about 30 degrees slant, facing south, and not obstructed by trees, other buildings, etc. This panel under ideal circumstances will be able to produce an average of its maximum.

Because the sun moves, cells are usually positioned within the panel at slightly varying angles so that the maximum number of cells at any given moment are perfectly aligned to produce their best results. This gives the panel a longer daytime running ability, rather than the usual 2-3 hours that flat cells would produce in daily. Other factors include loss of light through the glass covering, loss of power through the panel's conductivity, and so forth.

Expected Lifespan
The expected lifespan of a photovoltaic panel is usually given in years. Most solar panels have a 25-35 year lifespan, under normal conditions. If nothing physically harms the panel, it will likely last at least its expected lifespan. Most find that theirs last another two to three years beyond that, depending on the quality of the panel's construction.

Photovoltaics in the Northwest
Most photovoltaic systems (solar panels) require direct or near-direct sunlight to generate power. The less sunlight there is, or the more cloud cover there is, the less efficient the panels will be.

Even with fewer days of sunlight in western Washington and Oregon, there still is enough Solar Factor to make Solar work. Many new laws and incentives that have recently been added to encourage Renewable energy. Taking advantage of these incentives can help you on your way to lower monthly energy costs.

On the other hand, Washington residents have two other things to consider: Net Metering and tax deductions.

Washington State law requires utilities to pay the Solar PV customer for the amount of power their system produces. If your system and components are made outside the state of Washington the feed-in tariff is .15 cents per KW/HR. If your Solar system has an inverter made in the State of Washington but not Washington made panels then the tariff is .18 cents per KW/HR. If your system has Solar panels made in the State of Washington but not the inverter then the Feed-in tariff goes up to .36 cents per KW/HR. Lastly if your system has Solar panels and Inverter made in the state of Washington the feed-in tariff would be .54 cents per KW/HR. These incentives are set to expire under current law in year 2020.

The Federal Tax credit for Solar Energy systems is 30% of the cost of the installation and materials (with no maximum credit) This law is set to expire in year 2016. Consult your tax professional for further information. This credit takes a huge chunk out of your initial investment.

Solar Photovoltaic systems have a wide ranging ROI based on the extensive different rebates, tax incentives, feed-in tariffs. The ROI Could be as low as 10 years and up to the typical range of 16-22 years.

In the Portland area, the rating on that 0-10 scale of efficiency (sunlight) is higher (about 5.5). So ROI could happen faster. The credit is based on wattage ($3/watt) and has a maximum of $6,000, which is amortized over time ($1,500/year). So a 2,000 watt system would receive a $1,500 credit over four years for the building's owner. A typical Portland-area system could expect full ROI within 6 to 10 years.




How Solar Thermal Systems Work

Most solar thermal systems are used to heat water for both appliance use (dishwashers, showers, washing machines, etc.) and for heating (radiant floor, baseboard, or hot air transfer). Many are used for both to maximize their payoff.

Solar Thermal Panels
Solar thermal panels look very much like photovoltaic panels, except they do not have individual solar cells within them. They are usually thicker (taller) and are often darker. They work very simply.

Compare them to a garden hose left in the sun. When you tip the hose and pour the water from it, the water is often hot. That heat was collected through the hose from the sun. That is basically how solar thermal panels work.

The panels are positioned so that they can take maximum benefit from the sun as it shines down on them. They work whether there is full sunlight, partial sunlight, cloud cover, etc. Because of this, when compared to photovoltaic panels, solar thermal panels often have a much higher efficiency.

Most thermal solar systems in Portland and Seattle do not heat water directly, but instead use an anti-freeze solution which heats up, travels to the water or air source to be heated, and moves around it to heat by convection. Coils of pipes will surround a hot water pipe, for instance, and heat the water within by conveying heat from one pipe to another. This way the anti-freeze never comes in contact with the water.

This allows the system to function no matter what the temperature outside may be.

There are two basic types of solar thermal systems: Active and Passive. Both are eligible for tax credits at the state or county level. In Washington, Clallam, Clark, Franklin, and Grays Harbor have tax rebates for solar thermal installations. In Oregon, there are state rebates for both water heating and space heating (individually or combined).

Active Systems
An active system uses pumps to move liquids from the panels to where the heat is used or transferred, and back. These systems are the most common and generally are the most efficient. Using sensors, valves, and electronic controls, they can send hot liquid where it's needed, regulate how much is circulating, and accommodate changes in temperature outside. They also often have solar sensors so that the system drains off the roof and shuts down at night or in the dark.

Although these active systems sound complicated, they are generally very simple. The addition of pumps and sensors merely makes them more efficient. An active system in an average home can often expect a return on investment of 5-7 years and a total lifespan of up to 20 years, with proper maintenance.

Passive Systems
These systems are most common where it rarely freezes. They are not common anywhere but the most southern part of the United States and definitely not in the Northwest. These systems heat water directly and use a system of valves, pressure and gravity to circulate water between the home's water system and the solar thermal panels.

Hot water from the panels builds pressure and, when a valve senses that it is high enough, the water is released down into the home, creating pressure and leaving behind a vacuum. This moves cold water from the water system up into the panels. The valve closes when pressure lowers to a set point, allowing the cold water to sit in the panels and heat up.

In areas where a passive system is used, it is usually hot enough through most of the year for this cycle to happen several times daily. Passive systems are cheaper to install and easier to maintain, but are generally only useful in areas that gain minimal benefit from the energy savings regardless.

Passive systems can expect to achieve ROI in 5-9 years (depending on how often they are offline due to temperatures) and have a life expectancy of about 20 years.