Stand-alone Power Supply and Heating Systems
An individual’s carbon footprint is mainly decided by energy consumed to run various household appliances and energy used for home heating. Electric power supplied to grid-connected households is mostly derived from fossil fuels, and thus leads to greenhouse gas (GHG) emissions. However, homes in remote areas cannot afford grid power supply, and they use renewable natural sources available to them such as solar power, wind power, hydroelectric power or geothermal energy. Even, houses that can be connected to the power grid can opt for stand-alone power systems to reduce GHG emissions.
Most common form of off-grid power system is the solar photovoltaic (PV) system. It comprises of solar PV panels installed on the roof top (number of panels is based on the power requirement), batteries to store generated power, inverters to convert DC power stored in the battery to AC power, charge controllers, power conditioning and safety equipment, meters, and other instrumentation (US Department of Energy [DOE], Off Grid, 2016). Sun light is available only during daytime, so backup storage batteries are essential to store excess power generated from the PV panels, and supply power during nighttime (EECA, 2015). Also, when the solar power output is not sufficient to run electrical loads in the home, power from the battery can be utilized. Further, as voltage output from PV panels varies considerably, conditioning equipment is essential to protect appliances from power fluctuations. Usually, in remote locations renewable power systems are backed up with diesel generators.
Wind turbines and water turbines are also used to generate power based on the availability of wind with sufficient velocity or water flowing at sufficient force in certain areas (Energy Efficiency and Conservation Authority [EECA], 2015). The mechanical energy of rotating turbines is converted to electrical energy and used for home power supply. But, wind velocities as well as water flows are not constant and there is usually huge variation in the output power (EECA, 2015). Hence, similar to solar power system, power storage and conditioning is essential to use these forms of renewable power. Hybrid off-grid systems with a combination of solar PV panels, wind/water turbines are also installed in remote areas (Burch, 2001). Hybrid systems, have added advantage i.e. even when sunlight is not available during nighttime or on cloudy days, wind/water can drive the turbine and generate power.
Solar heating systems with flat plate or evacuated tube type collectors can be employed for home heating (DOE, Off Grid, 2016). Solar energy is used to heat up water or antifreeze liquid circulated in the collectors. Pumps and controllers are used to circulate the working fluid (water). The heat from working fluid is transferred to the distributing fluid in a heat tank, which is sometimes pressurized to attain a desired temperature (DOE, Off Grid, 2016). Distributing liquid from the tank then circulates through pipes embedded in the floor, radiating heat into the home space. Solar heating systems can be combined with solar PV panels to supply electric power to blowers, pumps or other electrical components of the heating system (DOE, Off Grid, 2016). Thus, a completely renewable power based space heating system can be installed in homes.
Geothermal heat pumps can be employed in regions where winter temperature can reach very low values. Below ground temperature is fairly constant and ranges from 7°C to 21°C based on the latitude. Geothermal heat pumps basically consist of a ground loop system, pumps and distribution system (Geothermal Heat Pump Association of New Zealand [GHPANZ], 2016). The ground loop system can be horizontally or vertically installed below the ground (DOE, Geothermal Heat Pump, 2016). Refrigerant is pumped into the loops and it gets heated up. Heated working liquid is then directly circulated in piping buried below floor, or some times a heat exchanger is used to transfer heat to a circulating fluid. Closed loop geothermal heat pumps are buried in a water body near to the house, and water recirculates in this system (DOE, Geothermal Heat Pump, 2016). In open loop system separate water intake wells and recharge wells are required to take up water, and return it back to the ground (DOE, Geothermal Heat Pump, 2016).
All renewable power systems mentioned above reduce dependence on grid power supply, and minimize the household carbon footprint (Gibson, 2011). Though these off-grid systems require high initial investment, running cost is cheaper as they have long life times ranging from 25 -50 years. One can get 10 – 15% return on investment annually within few years of installation, and there are government rebates available for clean power installations in several countries (Gibson, 2011). Thus one can use a stand-alone renewable power or heating system and remain independent as well as sustainable.
References
Burch, G. D. (2001, August 21). Hybrid Renewable Energy Systems. Retrieved April 16,
2016, from https://www.netl.doe.gov/publications/proceedings/01/hybrids/Gary Burch 8.21.01.pdf
DOE. (2016). Off-Grid or Stand-Alone Renewable Energy Systems. Retrieved April 15,
2016, from http://energy.gov/energysaver/grid-or-stand-alone-renewable-energy-systems
DOE. (2016). Geothermal Heat Pumps. Retrieved April 15, 2016, from http://energy.gov/
energysaver/geothermal-heat-pumps
EECA. (2015, September 24). Stand alone power systems (SAPS). Retrieved April 15, 2016,
GHANZ. (2016). Retrieved April 15, 2016, from http://www.nzgeothermal.org.nz/
ghanz_heatpumps.html
Gibson, S. (2011, March). Heat Your Home With Solar Hot Water. Retrieved April 15, 2016,
