Microgeneration is the small-scale production of heat or electric power from a "low carbon source," as an alternative or supplement to traditional centralized grid-connected power. Microgeneration technologies include small-scale wind turbines, micro hydro, solar PV systems, microbial fuel cells, ground source heat pumps, and micro combined heat and power installations. These technologies are often combined to form a hybrid power solution that can offer superior performance and lower cost than a system based on one generator.
History In the United States, Microgeneration had its roots in the 1973 oil crisis and the Yom Kippur War which prompted innovation. On June 20, 1979, 32 solar panels were installed at the White House. The solar cells were dismantled 7 years later during the Reagan administration, only to be replaced in the early 21st century. The use of solar water heating dates back before 1900 with "the first practical solar cell being developed by Bell Labs in 1954." The "University of Delaware is credited with creating one of the first solar buildings, “Solar One,” in 1973. The construction ran on a combination of solar thermal and solar photovoltaic power. The building didn't use solar panels; instead, solar was integrated into the rooftop."
Technologies and set-up
Power plant In addition to the electricity production plant (e.g. wind turbine and solar panel), infrastructure for energy storage and power conversion and a hook-up to the regular electricity grid is usually needed and/or foreseen. Although a hookup to the regular electricity grid is not essential, it helps to decrease costs by allowing financial recompensation schemes. In the developing world however, the start-up cost for this equipment is generally too high, thus leaving no choice but to opt for alternative set-ups.
Extra equipment needed besides the power plant
The whole of the equipment required to set up a working system and for an off-the-grid generation and/or a hookup to the electricity grid herefore is termed a balance of system and is composed of the following parts with PV-systems:
Energy storage apparatus A major issue with off-grid solar and wind systems is that the power is often needed when the sun is not shining or when the wind is calm, this is generally not required for purely grid-connected systems:
a series of deep-cycle, stationary or sealed maintenance free batteries (the most common solution) or other means of energy storage (e.g. hydrogen fuel cells, flywheel energy storage, pumped-storage hydroelectricity, compressed-air tanks, ...)
a charge controller for charging the batteries or other energy storage For converting DC battery power into AC as required for many appliances, or for feeding excess power into a commercial power grid:
an inverter or grid-interactive inverter. The whole is also sometimes referred to as "power conditioning equipment"
Safety equipment Groundings, transfer switches or isolator switches and surge protectors. The whole is also sometimes referred to as "safety equipment". Usually, in microgeneration for homes in the developing world, prefabricated house-wiring systems (as wiring harnesses or prefabricated distribution units) are used instead. Simplified house-wiring boxes and cables, known as wiring harnesses, can simply be bought and mounted into the building without requiring much knowledge about the wiring itself. As such, even people without technical expertise are able to install them. They are also comparatively cheap and offer safety advantages.
battery meters (for charging rate and voltage), and meters for power consumption and electricity provision to the regular power grid
Wind turbine specific
With wind turbines, hydroelectric plants, ... the extra equipment needed is more or less the same as with PV-systems (depending on the type of wind turbine used), yet also include:
a manual disconnect switch foundation for the tower grounding system shutoff and/or dummy-load devices for use in high wind when power generated exceeds current needs and storage system capacity.
Vibro-wind power A new wind-energy technology is being developed that converts energy from wind energy vibrations to electricity. This energy, called Vibro-Wind technology, can use winds of less strength than normal wind turbines, and can be placed in almost any location. A prototype consisted of a panel mounted with oscillators made out of pieces of foam. The conversion from mechanical to electrical energy is done using a piezoelectric transducer, a device made of a ceramic or polymer that emits electrons when stressed. The building of this prototype was led by Francis Moon, professor of mechanical and aerospace engineering at Cornell University. Moon's work in Vibro-Wind Technology was funded by the Atkinson Center for a Sustainable Future at Cornell. Vibro-wind power is not yet commercially viable and in early development stages. Significant progress will be needed to commercialize this early stage venture.
Possible set-ups Several microgeneration set-ups are possible. These are:
Off-the-grid set-ups which include: Off-the grid set-ups without energy storage (e.g., battery, ...) Off-the grid set-ups with energy storage (e.g., battery, ...) Battery charging stations Grid-connected set-ups which include: Grid connected with backup to power critical loads Grid-connected set-ups without financial recompensation scheme Grid-connected set-ups with net metering Grid connected set-ups with net purchase and sale All set-ups mentioned can work either on a single power plant or a combination of power plants (in which case it is called a hybrid power system). For safety, grid-connected set-ups must automatically switch off or enter an "anti-islanding mode" when there is a failure of the mains power supply. For more about this, see the article on the condition of islanding.
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