Introduction
Random page for thoughts regarding self sufficient / sustainable power.
Energy Generation
Some options for energy generation.
Solar
A number of methods exist for harnessing the power of solar,
Photovoltaic
Conventional method of generating electricity directly from the sun using 'solar panels'.
General efficiency of around 13 to 15% (1m² will generate ~150W).
Details regarding this option should be investigated.
Concentrated Photovoltaic
Mirrors etc used to focus more sunlight onto Photovoltaic (PV) cells.
Details regarding this increase to efficiency could be investigated.
Concentrated Solar Power
Light from the sun is concentrated (usually via mirrors or lenses) to heat a liquid (usually oil or a molten salt). The heated liquid is usually used to boil water and drive a steam turbine or Sterling engine to generate electricity.
Sandia National Laboratories National Solar Thermal Test Facility produces as much as 25 kW of electricity, with a conversion efficiency of 31.25% from a single solar dish-Stirling engine system.
Details regarding this option should be investigated.
Hydroelectricity
Limited to suitable location.
Temperature difference between Environment:
Difference Between Ground Temperature and Air
Options for this included via the thermoelectric effect (i.e. Peltiers) or Sterling engine.
Peltiers:
Peltiers have poor efficiency (~10%)
Peltier costs from www.ebay.com.au as of 16/08/2012:
60W, $3.94
136.8W, $5.32
154W, $5.98
Details regarding this option should be investigated.
Sterling Engine
A Stirling engine is a heat difference engine. Need to determine if this is a practical option.
Details regarding this option should be investigated.
Radioisotope Thermoelectric Generator (RTG)
The heat from radioactive decay of a radioactive material is used to generate heat which is converted to electrical energy via the Thermoelectric effect.
RTG systems have poor efficiencies (~3 to 7%) and the radioactive material required makes these poorly suited for individuals.
http://www.its.caltech.edu/~jsnyder/thermoelectrics/history.html
http://www1.eere.energy.gov/vehiclesandfuels/pdfs/thermoelectrics_app_2012/wednesday/fleurial.pdf
https://netfiles.uiuc.edu/mragheb/www/NPRE%20402%20ME%20405%20Nuclear%20Power%20Engineering/Radioisotopes%20Power%20Production.pdf
http://www.ne.doe.gov/pdffiles/MMRTG_Jan2008.pdf
Solar Efficiency
At the top of the atmosphere there is approximately 13666 W/m² of energy available from the Sun. This figure takes into account the whole solar radiation spectrum.
After travelling through the atmosphere however this figure is reduced to ~1000 W/m². (To be confirmed).
When using solar energy there are a number of factors that should be considered that can effect the energy produced, these include
Image taken from: http://www.yourhome.gov.au/technical/fs67.html
- Temperature (PV cells produce less energy as their temperature increases)
Efficiencies for solar cells are quoted at STC or PTC
- STC = Solar irradiance of 1000 W/m², solar spectrum, airmass of 1.5, cell temperature of 25°C.
- PTC = Solar irradiance of 1000 W/m², solar spectrum, airmass of 1.5, ambient temperature of 20°C, wind speed of 1m/sec (PTC stands for "PV USA Test Conditions").
Energy Storage
Batteries
Initially thoughts are that batteries are expensive and have fixed service life (wear out) which I find undesirable.
However batteries may be an acceptable solution.
Details regarding this option should be investigated.
Compressed Air
Store excess electrical energy as compressed air by compressing air with an electric compressor.
The potential energy of the compressed air could be released to power a turbine to generate electricity.
Details regarding this option should be investigated.
Hydrogen
Generated via electrolysis of water to generate Hydrogen.
Hydrogen could be converted to electricity via fuel cell/s, by being burnt to heat water to power a steam turbine or by driving an hydrogen engine to power a generator.
Details regarding this option should be investigated.
Heat
Potential energy could be stored as heat such as in oil or molten salt.
Details regarding this option could be investigated.
Pumped Water Storage
Water can be pumped to a height with excess electrical energy.
The potential energy of the water could be released to power a generator (normally the pump being driven reverse).
Limited to a large extent by suitable location.
Things to Research
- How is solar panel efficiency measured?
- Batteries (Cost, capacity required, physical size & weight, lifetime, etc)
- Compressed air as an energy storage method (energy density, efficiency, method to convert to electricity)
- Hydrogen (production, storage, etc)
- Ground temperature vs air temperature (real data, heat transfer to / from ground)
- If Peltiers would be viable for electricity generation (real world power output)
References
A4_4 An RTG Powered Home.pdf
h2homesystem.pdf
soil temp.pdf
http://www.tellurex.com/technology/peltier-faq.php
http://sroeco.com/solar/most-efficient-solar-panels
http://worldinashell.net/
http://inhabitat.com/wind-and-sun-powered-shipping-container-unfolds-into-traveling-cultural-exhibition/
http://www.phys.unsw.edu.au/~map/weather/barometer/soil_temperature_profile.html (Ground Temperature)
http://tomswiki.wetpaint.com/page/Peltier+%28TEC%29+Cooling
http://www.overclockers.com/peltier-basics/
http://en.wikipedia.org/wiki/Sunlight
http://en.wikipedia.org/wiki/Insolation
http://en.wikipedia.org/wiki/Irradiance
http://www.acrim.com/ (Total Solar Irradiance (TSI) Monitoring)
http://en.wikipedia.org/wiki/Concentrating_solar_power
http://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator
http://en.wikipedia.org/wiki/Solar_panel
http://www.yourhome.gov.au/technical/fs67.html
http://www.partsonsale.com/stc1.html
AS4509 Stand-alone Power Systems (Australian Standard)
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