HOME & RENEWABLE ENERGY
Conservation
Conserving energy is a smarter financial investment than renewable energy. Only after you've made your home as efficient as possible by air-sealing, insulating, upgrading/ maintaining utility systems and appliances, and reviewing your energy use habits, should you look at purchasing or generating renewable energy to reduce your dependence on fossil fuels and lessen contribution to climate change. Solar and geothermal are the renewable energy systems most appropriate for residential use.
Windsource™
Wind power is a clean energy source. If installing renewable energy isn't an option for you, purchase clean energy credits (sometimes called wind energy credits) from your electric utility provider. While it doesn't mean you're electricity specifically is generated by wind power, this forces electric utility providers to develop wind generation capacity above and beyond mandates, and supports wind farms in our area. Buy renewable energy through Xcel's Windsource program.
Solar
If a site has access to solar resources, solar energy harnesses the sun's heat to either generate electricity (photovoltaic or PV) or to transfer thermal energy (thermal) to heat air and water in our home. These strategies are called active solar, as opposed to passive solar, and require the installation of solar panels on a track, wall or roof. Which type of solar energy system, thermal or photovoltaic, you should use on your home is dependent on specific site conditions.
To determine if your home is a candidate to use active solar technologies, you will need a solar site assessment.
STEP 1:
Before getting a professional assessment, here are a few things you can determine on your own:
- Do you have a south-facing wall or roof area where you could place solar panels? If the answer is no, do you have a large yard area, exposed to the south, where you could install track or ground mounted panels?
- Is the wall/roof/yard area free of trees or shade from nearby buildings?
STEP 2: Get a professional site assessment & selecting an installer: Most solar site assessments are done by solar installers. When contacting installers, determine whether or not they are certified by North American Board of Certified Energy Practitioners (NABCEP) . This organization sets standards for installers, ensuring you as a customer are working with a knowledgeable, skilled solar contractor. Ask how much a site assessment costs and what is included in the assessment. For detailed questions to ask your installer, view the Division of Energy Resources's document, "Questions to ask a Renewable Energy Installer."
Professional installers will be able to determine which type of solar system is appropriate for your site. They will also be able to tell you how much space you will need and how much energy will be generated by the system installed. Be sure to provide information on your electricity consumption in kWh and your natural gas consumption in therms (by month) and they can provide details on what portion of your current use can be replaced by the system they propose.
STEP 3: One of the biggest challenges to installing solar technologies is cost. Utility and government incentives can help make solar energy more affordable.
Solar Thermal Air
Solar air heaters are typically the most cost-effective solar technology with the shortest pay-back. They use air as the medium to transfer heat from solar radiation to the air in your home. They work best on a vertical surface and can be integrated into walls and used as either individual room heaters or to supplement a whole-house heating system. Collector plates absorb solar radiation and heat the air inside the collector. Active solar collectors use standard HVAC motors and fans to push the heated air into a room or duct system. As the warm air leaves the collector, cool air is drawn in and heated. Warm air entering ducts can be directed to a heat recovery system; the pre-heated air from the solar collector lessens the burden on traditional heating systems.
Solar Thermal Water
Solar thermal water heaters are a cost-effective solar technology. Depending on available incentives and fuel prices (of the device which the solar thermal water is replacing/ supplementing), solar thermal water payback period, varies widely. Solar thermal collectors an air space, water, or anti-freeze fluid called glycol which in turn heats water used in the home. Our cold winters mean freezing is an issue, so indirect solar thermal water systems (those that use glycol) are more common. When used as a domestic hot water supply, indirect systems pump glycol fluid into a heat exchanger where it transfers the heat to the domestic hot water storage tank.
Typically installed on roofs, solar thermal collectors are available as either flat-plat or evacuated tube collectors. Flat plat collectors are a weatherproof box with an absorber plate to collect solar radiation. The absorber plate transfers heat into fluid filled pipes underneath it; the fluid then flows to the heat exchanger. Evacuated tube collectors utilize glass tubes to absorb and transfer heat. Each tube has an inner and outer tube. Air between the tubes is removed to prevent heat lost through conduction and convection. The inner tube is usually coated or made of a different material to absorb solar radiation. The heat is then transferred to a heat exchanger. All solar thermal water systems should be connected to a standard water heating system for a back-up hot water supply for cloudy days when sunshine cannot be captured. Learn about installing solar thermal water on your home.
Solar Electric Photovoltaic
Solar electric photovoltaics (PV) have the longest pay-back of the common solar technologies. PV panels are used to convert solar radiation into electrical energy. Typically installed on roofs or tracks, the panels are made of PV "cells" connected to a converter which is in turn connected to your home. Panels installed on "tracks" can be programmed to follow the sun, to collect as much solar radiation as possible throughout the day. If you're considering re-roofing your home, consider using PV integrated roof shingles to generate power for your home.
PV panels are suitable for year-round use and are low maintenance. Many panels operate for 30 to 50 years! PV technology is constantly evolving, and panel efficiency is increasing.
Wind Turbines
Although Minnesota as a state has great potential for wind source energy supplies, residential scaled wind turbines in our urban area are not a viable energy source. Wind power systems need large, open areas where a turbine can be installed at a substantial height in order to reach constant, viable wind speeds. In addition, many urban areas have regulations on wind power system installation.
If you live in a rural area and are considering investing in a wind power system, read the Small Electric Wind Systems document assembled by State of MN to learn more about wind power and to determine if your home is a viable candidate.
Providing energy back to the grid
When installing electricity generation to your home, contact your utility company as soon as possible for details on inter-connection costs and requirements, as well as the price they pay to purchase electricity. This process will take some time, so begin as soon as possible. Verification of meeting these requirements should be part of the final inspection and certification process. While your installer may handle this, do not assume that they will without confirmation and including this in the installation contract.