Solar Powered Housing
With the increasing energy consumption rates and increasing pollution rates as a result, it is important for our society to focus on cleaner, more renewable energy sources. Because households are a major consumer of energy throughout the world, families could contribute greatly to the use of renewable energy sources through the use of solar home systems. If more and more people agree to the use of solar home systems, our fossil fuel consumption rates will drop and we will notice profound improvements throughout our environment. This essay will discuss various topics that are necessary in order to understand the function of a solar home system.
First, for a solar home system to function effectively, one must first reduce the amount of energy consumed within the house. This can either be achieved through efficient house design or through efficient energy consumption. Efficient design features include proper sealing of windows, doors, and cracks, proper insulation, proper window design for passive heating, proper air infiltration, and the use of proper materials for heat absorption. By designing your house efficiently, you greatly reduce the amount of energy consumed and therefore reduce the cost and size of your solar home system.
Efficient energy consumption is also extremely important when using a solar home system. Energy consumption can be greatly reduced by such acts as buying efficient appliances, keeping doors and windows closed to reduce heat loss, turning off lights and appliances when they are not needed, and turning down A/C levels. These acts also contribute greatly to a reduction in the size and cost of your solar home system.
The basic idea behind solar home systems is that they take energy from the sun and turn it into electrical energy to be used throughout the household. The cells that collect the sunlight are called photovoltaic cells. They consist of two differently charged surfaces, usually made of silicon, a metallic grid that connects the two surfaces together, an antireflection coating, and a protective glass cover. To create the electric current, the cells take advantage of the fact that light can knock electrons out of the atoms of certain substances. To make this happen, the cells first absorb the photons from the sunlight they are exposed to. These photons then cause the electrons from the positively charged surface to bounce to the negatively charged surface creating an electric current. This direct current is then carried by wires away from the photovoltaic cells and through an inverter that transforms the current into an alternating current so it can be used in the house (U.S. Department of Energy).
There are two different types of silicon cells that can perform this function; thin-film and crystalline. Thin-film cells are generally less expensive but are also less efficient and don’t last as long. They tend to have a 10% efficiency rate for converting sunlight to electricity. Crystalline cells, on the other hand, are more expensive but have increased efficiency and durability. They tend to have a 20% efficiency rate for converting sunlight into electricity. Even more efficient cells (40%) are in the process of being developed, however, are currently too expensive for typical use (Architectural Record).
Each individual cell tends to be very small and produces only a small amount of energy. These cells are therefore combined together to form modules or panels that can produce anywhere from a few milliwatts to several megawatts of energy. These modules are measured in terms of “peak watts”. This refers to the maximum output of the module under peak sun condition or conditions where sunlight gives off 1000 watts of energy per square meter. “Sun hours” or “insolation”, refers to the number of hours an area experiences peak sun conditions. In North America, we average about 3 to 4 peak sun hours per day in the summer. Equatorial regions can average above 6 peak sun hours per day. Consequently, the benefit and efficiency of a solar home system is greatly determined by the area in which it is being used (Advanced Energy Group).
There are many different parts to a solar home system. A basic solar home system will include a PV module, a charge controller, a battery, an inverter, wiring, fluorescent lights, and outlets for other appliances. The first part, the module, must be orientated appropriately to absorb the most amount of sunlight. The most efficient orientation for North American users is direct south. This allows the module to absorb light throughout the day. To determine true south, you can divide the span of time between sunrise and sunset and true south is the position of the sun at that time. The angle of the module should be set anywhere from the degree of your latitude to plus or minus 15 degrees depending on when you consume the most energy. To capture more energy in the winter, you should set the module to minus 15 degrees. Plus 15 degrees will allow you to capture more energy in the summer. For the best yearly position, one should simply set the module at the degree of his latitude. Another even more efficient approach, however, can be to use a module system that has the ability to move and track the sun. This will capture the most amount of sunlight possible during all times of the day and year (Advanced Energy Group).
The next part, the charge controller, is used to control the flow of energy between the module, the battery, and the loads or appliances. This feature will cut off electricity flow to the battery when it is fully charged and cut energy drainage from the battery when it reaches low levels. The charge controller also has a meter that displays the relative state of charge of the battery (Advanced Energy Group).
The third part is the inverter. The inverter is used to convert the D/C current from the module into an A/C current so it can be used by appliances in the house (Advanced Energy Group).
The fourth part is the storage battery. This battery is used to store the excess energy from the module during the day so it can be used to run appliances at night or when the sun isn’t shining. This battery is typically sized to provide several days of electricity in the event that overcast weather prevents recharging (Advanced Energy Group).
The fifth part is the fluorescent lighting. Fluorescent lights are usually included in all basic systems and can often provide more light than typical incandescent light bulbs. A basic small system may include 2 to 6 lights while a larger system may include 10 to 20 lights (Advanced Energy Group).
The last two parts of a solar home system are the wiring and mounting structure. The mounting structure is attached to your roof and supports the modules. The wiring carries the electricity from the module to the battery and to outlets throughout the house (Advanced Energy Group).
The next factor one must consider when thinking about installing a solar home system is what size system they need. There are typically three factors that contribute to determining the size of an SHS: environment, energy consumption, and desired energy contribution. The environment is important because it determines how much sunlight the module will be able to absorb and therefore, how much electricity it will be able to produce. Someone living on the equator, for example, will get more out of the same sized solar home system than someone living in a northern region that receives little sunlight. Therefore, the first thing one must determine is how much sunlight they expect to receive each year and how much electricity different sized systems should be able to produce. To make things more convenient, these numbers will often by provided for you by your SHS manufacturer (Advanced Energy Group).
The next thing one needs to determine is how much energy they consume. This can be calculated by examining your electric bills for each month and totaling the amount of electric energy you consume.
The final factor that one must consider is how much they want their SHS to contribute to their energy needs. One person may want their SHS to provide only a fraction of their energy needs while another person may want their SHS to cover all their energy needs. The amount of energy you want your SHS to contribute will determine the size of the system you need.
Once you have determined the yearly amount of energy you want produced by your SHS system, in kWh per year, you can divide this number by 1750 kWh, which is the average yearly output of a 1kW system. This will determine the size of the system you need (ex: .5, 1, 3 kW system). Small changes will need to be made to this size depending on the environment in which you wish to use it (Kyocera Solar, Inc).
After you have determined the size of the system, the next thing to determine is the cost. Solar home systems can range anywhere from a few thousand dollars, for a very small system, to over $40,000 for a very large system. However, this number is often misleading because of government incentives. People interested in installing a solar home systems can often seek government incentives in the form of tax credits, state grants, state rebates, low-interest loans, property tax exemptions, and sales tax exemptionsto lower the cost (Kyocera Solar, Inc). Some examples of incentive programs are The Department of Energy’s $1.5 million reserved for solar roof grants, UK grants that cover 50% of the cost of installing an SHS, and the California rebate program that covers 50% of the cost of an SHS. Therefore, a lot of incentives are available to help reduce the cost of solar home systems. With these incentives, an SHS can often be reduced to a low enough price to make it a good economic investment (SolarBuzz).
Another point to consider before getting an SHS is whether or not you can connect your SHS to the local utility grid. The importance of this is that unused energy can be sold back to the utility. During months when you don’t consume a lot of electricity, selling excess electricity back to the utility can make your SHS much more economical. For this reason, 34 states now have laws that require electrical utilities to allow solar home systems to be connected to their grid (SolarBuzz).
To get a better understanding of how an SHS can benefit a household, we’ll pretend we’re installing one in my home. My house is situated in northern New Jersey and consumes about 15,000 kWh per year at a cost of 10 cents per kWh, making the electric bill about $1,500 per year. However, after making my house more energy efficient, the energy consumption could easily decrease to about 10,000 kWh per year, making the electric bill about $1,000 per year or $84 per month. Over a 25 year period, my electric bill would then total to about $25,000.
The next thing I have to do is determine the size of the SHS. Let’s pretend I want my SHS to cover all of my energy needs throughout the year. By contacting Kyocera, an SHS manufacturer, I am able to receive the estimated energy production for various systems under my regions weather conditions. With this information, I will select the My-Gen 64. The My-Gen 64 is a 6.4 kW system that costs about $50,000 before rebates, is guaranteed for 25 years, would produce about 10,000kWh of electricity per year, and would eliminate 16,000 lbs. of CO2, 44 lbs. of SO2, and 30 lbs. of NOX emissions in the first year. Additionally, through government incentives, it is estimated that I could receive about $30,000 for my SHS making its total price only $20,000, or $75 per month for 25 years. If I was only able to receive only $25,000 in incentives, then the SHS would cost me about $90 per month for 25 years. When evaluating these numbers, we learn that the system’s cost is mostly determined by the amount of incentives I can obtain. If I get a full $30,000, the systemwill only cost about $75 per month, cheaper than my current electricity bill of $85 per month. If I am only able to receive $25,000 in incentives, then the system will cost about $90 per month, greater then my current electric bill. Nonetheless, I would still be greatly reducing the emission of harmful gases and reducing my reliance on fossil fuels. Consequently, even if the costs would be slightly above my current electricity costs, it is still a worthwhile investment when taking the environment into consideration. Furthermore, as solar technology increases and fossil fuel prices rise, using an SHS may become an even better economical decision (Kyocera Solar, Inc).
If you wish to take a step further and make your house truly energy efficient, you can follow the design of the North Carolina State University Solar House. This house was opened in 1981 and serves as an educational and demonstration showcase for solar and energy-efficient technologies. It also contains laboratories for solar research, houses extensive information libraries, and provides tours for those interested in solar power and energy efficiency. Some information on the house is that it is 2,000 sq. ft., has a total heating bill of less than $70 for the entire winter, uses a solar hot water system, uses a 3kW SHS, has a centrally located sunspace, uses earth berming, has two thermal solar walls, and has many additional energy efficient features. The solar hot water system in the house allows the water to get heated up by solar panels and by direct heat from the sun, reducing the need for electric or gas water heating. It also provides enough hot water for an average family of four people. The sunspace greatly reduces the need for space heating by collecting a large amount of solar heat in a central room and dispersing it throughout the house. The thermal walls also aid the heating process in the winter and the cooling process in the summer by holding in the hot or cold air. Finally, the earth berming provides a similar function by holding in heat in the winter and preventing heat gain in the summer. There are also many additional energy efficient features in the house that one can learn about by contacting the NCSUSolarCenter or by visiting their website (The North Carolina Solar Center).
In conclusion, solar home systems are a definite possibility as an energy source. Their basic function is to convert energy from the sun into an electrical current that can be used throughout the house. Because of our increasing consumption of fossil fuels and increasing pollution because of it, solar home systems may become a more and more popular source of household energy in the future. While they are currently somewhat expensive, numerous incentives can greatly reduce their price. Additionally, as technology increases and fossil fuel prices rise, solar home systems will become an even more economical investment. Consequently, one interested in aiding the environment and reducing the use of fossil fuels while still meeting their energy needs, should definitely consider the use of an SHS in their home.
Works Cited
About Photovoltaics. 25 October 2002. U.S. Department of Energy.
Advanced Energy Group. 1999-2002. <
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Nancy B. Solomon. Photovoltaic Technology Comes of Age. Architectural Record.
News – U.S. Department of Energy Awards $1.5 Million for Solar Roof Grants. 2
October 2002. SolarBuzz. <
PV System Calculator. 2 November 2002. Kyocera Solar, Inc. <
solar.com/index.html>.
Solar House. The North Carolina Solar Center. <
house.pdf>.
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