What do renewable energy power and heating systems cost?
In short, cost depends on the size of the system. System sizes can be constrained by practicing good energy conservation habits and efficiently taking advantage of the natural energy resources at your site.
The total cost of an independent power system can range from about $800 to $31,000, depending on the level of power you desire. Financial incentives such as rebates and financial incentives can lower the cost of a system by 30% to 50%. Extending the utility grid can cost $15,000 to $30,000 per mile.
Careful selection of appliances such as your refrigerator, washer and dryer, water pumps, cooking appliances, lighting, water heating, and home heating and cooling systems can lead to only needing 1/4 of the power of a typical household with less efficient systems. Using natural gas or propane for major heat production in cooking, water heating, clothes drier, and home heating methods such as passive solar, solar radiant floor heating or wood heat will result in much smaller electricity needs.
How do renewable energy power systems work?
Solar photovoltaic arrays and wind or hydro turbines convert sun or kinetic energy into direct current (DC) electricity. DC electricity is what is stored in batteries. Solar PV, wind, or hydro electric systems may be designed for 12 volt DC, 24 volt DC, or 48 volt DC.
To use the electricity generated by solar, wind, or hydro, it is either stored in batteries or fed into the grid.
For off-grid or battery based systems the DC power is stored in deep cycle lead-acid batteries or other high-performance batteries using a charge controller which controls the flow of power to the battery. To prevent battery damage from overcharging, the charge controller automatically cuts back or stops the charge when batteries become full. There may also be a meter to show the status of the charging process. Batteries will allow the user to draw power from storage, even during sunless, windless, or waterless periods. Power can be drawn slowly by light loads or quickly by heavy loads. The batteries can instantly supply large surges of stored electricity as needed to start or run heavy power appliances that the solar panels or hydro or wind system alone could not power. Typically, 2 to 12 square feet of batteries weighing 200 to 1000 pounds are enclosed in a battery box with a vent pipe to outside. The size of the battery bank depends on the characteristics of the system including surge power requirements and the amount of reserve power needed, because lead-acid batteries need to be frequently 100% fully charged (equalized) to remain in good condition. They should never be drawn completely down to empty. Because of these needs, to get the most years from your batteries requires some supervision/maintenance by the owner.
Most household appliances require AC power. However, DC appliances can be very energy efficient. Sometimes a small solar electric RV, boat, or cabin may use only DC wiring and appliances. Where AC power and appliances are needed, an inverter is used to convert the 12, 24, or 48 volt DC current from the battery into 120 volt AC current, the same as standard utility power for standard household lights, outlets, and appliances. Most solar homes use primarily 120 volt AC produced by the inverter. After conversion to AC, power from the inverter connects into the circuit breaker box of the house in place of utility lines. The house breaker box routes power to lights, appliances, and outlets of the house. Inverters for home power come in ratings from 50 to 5500 watts and are sized for the maximum combined load to be sustained.
Commonly a standby inverter is used in on-grid/off-grid applications. These inverters have a built-in battery charger and transfer relay; many will auto start a backup generator. When the input terminals of a standby inverter/charger receive power from an outside source of AC (a generator or utility power) the inverter stops producing AC power from the batteries, and instead passes generator or utility AC power straight through to the house. At the same time it uses the generator or utility power to recharge the batteries. Some standby inverters even auto-start the generator when batteries need charging. A separate battery charger can be used instead of (or in addition to) a standby inverter/charger.
When stored power is low or during a power-outage/shortage, an engine driven backup generator is used to recharge the batteries or provide direct power. The generator is shut down after the batteries have been recharged. The backup generator produces 120 volt AC power and also serves as a 2nd source of AC power such as during a temporary need for additional power for large loads like during construction.
Other components of a renewable energy system are fuses and circuit breakers, and meters for gauging how things are working, how much power is being generated and/or stored.
Off-Grid LIving DOs and DON'Ts:
Most household appliances and lights use only a little electricity, easily supplied by the sun, wind and, micro-hydro. Solar electric homes convert most of their power to 120 volt AC to use as needed for household appliances and lights. Most common are lights, water pump, TV-VCR-Satellite, computer, stereo, vacuum cleaner, kitchen appliances sewing machine, power tools and office equipment. Even high wattage appliances like microwave oven, hair drier, toaster and clothes washer consume little power because their actual running time is short. Various water pumps, including deep well pumps up to 1/2 horsepower, are used. Special design electric refrigerators and freezers save energy in a solar home; gas and small DC powered refrigerators are also used. Plug appliances into surge protectors that can be turned completely off. Many appliances draw electricity 24 hours a day as they sit unused in standby mode. Avoid most large refrigerators and freezers: standard, non-Energy Star rated refrigerators have poor insulation and run long hours every day. Most still use well over 1.5 kilowatt hours per day, over 450 kilowatt hours per year. Special electric refrigerators and freezers designed for solar powered homes use only half the power of conventional ones. Propane refrigerators and freezers require no electricity. Building homes with passive solar heat design saves heating fuel for the rest of the building's life. Useing passive or active solar such as south facing windows with mass floors, solar radiant in-floor heating, tankless gas or propane water heaters will make a big difference.
Don't use electric appliances with heat elements such as electric furnace, electric hot water, electric cook stove, electric heated clothes drier,or electric air conditioner. These types of appliances account for 80% of the typical household's electric bills. Other fuels produce heat at a much lower cost. Use wood or propane fueled furnaces; propane cook stoves and water heaters; use gas fired clothes dryers (or just a rope in the sun).