Passive and Active Solar Systems
Energy costs are high, and rising.
Understandably, homeowners are concerned about their skyrocketing utility bills. They want action! This is what you can do:
Combine a renewable power source such as solar energy with an energy efficient home to substantially reduce utility bills.
A solar home can look and function very similar to a conventional home, except that the energy bills are much, much lower. By employing simple passive solar design tactics -- such as orienting most windows to the south -- any style home can take advantage of the sun's energy. Active solar panels are typically mounted flush with the roofline to reduce the visual impact. There are even roofing products that serve the dual purpose of producing electrical power while blending seamlessly into the architecture.
Following are several methods for employing solar energy in modern homes.
Tech Set Details
Building a storm-resistant roof is the most important way to protect a home from damaged incurred by strong winds. Consider the following 11 recommendations, especially if you are building in an area that is likely to be hit by strong winds.
Passive solar design uses architectural features, not special equipment, to minimize mechanical heating, cooling, and lighting needs. Examples include using south-facing windows to allow sunlight to enter the home, masonry or other materials to absorb thermal energy, overhangs to shade windows, and windows, tubular skylights, or skylights placed strategically for natural lighting and cooling with prevailing breezes. Although passive solar designs do not require high-tech gadgetry, they do require a designer who is knowledgeable about solar geometry and building material selection.
View the Lighting Tech Set for additional passive solar design strategies by
using natural lighting
Translucent wall and ceiling panels make it possible to create structural walls and skylights that permit diffuse natural light to enter the home. Translucent panels typically have higher R-values than traditional windows and skylights, but lower R-values than conventionally constructed walls and roofs. The commercial construction industry has embraced them to provide natural daylight to interior spaces, a favorable interior environment, and reduced artificial lighting needs without compromising privacy and security.
Solar Water Heaters
Solar water heaters come in a variety of configurations. A solar water
heating system usually consists of a hot water storage tank, a solar collector that absorbs solar energy (often mounted flush to the roof), and (for forced circulation systems) a pump and controls. Most systems have back-up water heating such as an electricity or gas tankless water heater. Solar water heaters can heat up to 100 gallons of hot water a day. A Federal Tax Credit offers to pay 30% of the installed cost up to $2,000 through 2007.
Solar electric or photovoltaic (PV) systems convert solar energy directly into direct current (dc) electricity. An inverter converts the PV-produced direct current to common household current (ac). When a PV system is connected to the utility via the electric meter, the PV system can send power back to the utility grid when it is not needed in the home-which may reverse the direction of the meter. PV systems usually cost between $8,000 to $10,000 per kW, less the numerous federal and local rebates. An average 2 kW system will provide roughly half of a home's electric demand.
Photovoltaic cells can now be built into roof shingles. Different types of photovoltaic panels and their attributes are explained in DOE's publication, PV Systems.
PV systems typically require specialty installers who can design and install the various components of the system.
Photovoltaic Solar Safety Lighting
A vast variety of solar garden, spot and safety lights are commercially available. Using PV cells integrated into the light casing, solar lighting can be placed nearly anywhere without the restrictions of wiring.
Eight simple steps and you're on your way to greater energy freedom.
Review applicable building codes
Chapter 23 of the International Residential Code briefly covers solar systems. It states that solar systems and storage units must be listed with an approved testing agency, and heat transfer fluids cannot be flammable.
In some communities, solar collectors that can be seen from the street may be subject to neighborhood covenants and conditions. Review Homeowner's Association documents.
Eliminate unnecessary electric loads
Maximize the home's energy efficiency and reduce electrical demand before implementing solar strategies. In most cases, it is more cost effective to improve energy efficiency than it is to add solar energy capacity. See the fact sheet Considerations for Building a More Energy Efficient Home, for basic information about energy efficient home construction.
Take advantage of solar energy during the design process
Maximize a home's use of solar energy with good siting and architectural features, which adds little or nothing to the cost of the house. Select materials that suit the climate. This step may require the help of an architect who is knowledgeable about solar design. Passive Solar Design, a U.S. Department of Energy fact sheet contains basic design guidance.
Courtesy of the NAHB Research Center
Identify financial incentives for active renewable energy systems in your area
Incentives can drastically improve the economics of using solar energy. Consult the Database of State Incentives for Renewable Energy and the Tax Incentives Assistance Project website for both Federal and State incentives.
Find local businesses that are experienced in solar energy system design and installation
Consult the yellow pages or try an online energy business directory such as http://energy.sourceguides.com/.
Determine the available solar resource
Solar Radiation Basics provides basic information about the solar resource. Insolation maps and weather data are available to determine the output of solar systems across the country. Also consult PVWatts, a program that calculates the output of a PV system.
Examine strategies for solar water heating
Consult with local businesses and installers to examine the costs and benefits of solar hot water systems. Basic information about solar water heating systems, including sizing, can be found in Heat Your Water with the Sun, A Consumer's Guide. The Solar Rating and Certification Corp. (SRCC) maintains a testing, rating, and certification program for solar water heating systems. The SRCC has developed a set of annual energy savings data and estimates the annual energy savings for major cities.
Identify strategies for solar electric systems
Consider small systems to manage critical or remote loads. Use information including the expected electrical output of the PV system, initial system cost, and anticipated electric cost savings, as well as local and state financial incentives and any limiting site conditions (e.g., shading from mature trees, no southern exposure) to determine the best PV system for the home.
Installing solar thermal or PV panels on a roof will require an analysis of the design load of the roof and the weight of the equipment that will be installed. On existing roofs, framing members can often be reinforced from within the structure if necessary. Most PV or solar thermal collectors do not require additional structural support, but integrated collector storage (ICS) systems store water within the collector and, therefore, have a heavier design load.