Emerging technologies are relatively new to the distributed generation market in California, yet have demonstrated significant potential for greenhouse gas emissions reductions.
Storing energy can be just as beneficial as producing it. Energy storage systems convert electricity into another form of stored energy and then convert it back to useful energy at a later time in the form of electricity or thermal energy.
Distributed energy storage technologies have a number of economic advantages. For example, grid-tied batteries are capable of reducing utility demand charges and “load shifting,” that is, storing electricity from the electric grid during off-peak hours when electricity is cheap and discharging the electricity during peak hours when electricity prices are more expensive. Similarly, thermal energy storage systems use electricity during off-peak hours to chill or freeze water in order to cool air and provide air-conditioning or refrigeration during peak hours. Energy storage systems can be coupled with intermittent generation technologies such as solar and wind power to provide a continuous supply of renewable energy to a home or business.
A fuel cell is a device that converts the chemical energy in hydrogen into electricity through an electrochemical reaction. The hydrogen used to power the fuel cell may come from a variety of sources, including natural gas, waste gas or biogas. A single “cell” is only able to create a small amount of electricity; therefore multiple cells are stacked together to produce power as needed. Some fuel cell systems recover the waste heat generated by the process to be used in another process. Fuel cells are highly efficient and useful for many industries and applications.
Biogas is a renewable fuel that is derived from the breakdown of organic matter. Biogas can be used to fuel Self-Generation Incentive Program technologies such as microturbines, combustion engines or fuel cells at the location the biogas is produced, such as a wastewater treatment facility. Alternatively, biogas may be delivered to customers via a natural gas pipeline. Generators that utilize either on-site or pipeline directed biogas are eligible for additional incentives.
Renewable and Waste Energy Recovery
Renewable and waste energy recovery technologies take advantage of inherently available wind, heat or pressure resources at a particular location by directing it through a turbine to generate electricity. The following technologies are 100% carbon-free ways to produce power.
Wind is created when differences in atmospheric pressure areas give rise to air movement. When airflow passes through the blades of a wind turbine, the kinetic energy of the wind turns into mechanical energy as the blades turn a shaft that powers an electric generator, creating electricity. Wind resource maps are available to help developers locate the most effective areas for wind energy generation.
Waste heat to power systems recover excess heat from an existing industrial process that would otherwise be released into the atmosphere and convert it into usable electricity. The organic Rankine cycle turbine is an example of a waste heat to power generator system whereby the captured heat is used to vaporize an organic fluid that spins the blades of a turbine and drives an electric generator.
Pressure reduction turbines generate power from the reduction in pressure in water pipelines, natural gas pipelines or steam systems. The water, natural gas or steam is directed through valves that press against the blades of a turbine, which powers an electric generator and converts mechanical energy into electrical energy. Pressure reduction turbines are best suited for existing industrial processes such as at a water treatment facility or desalination plant, where the pressure patterns are easily predictable.
Conventional Combined Heat and Power (CHP)
Combined heat and power is the simultaneous production of electrical and thermal energy from a single source. The dual benefit of using fuel to generate both heat and power make CHP systems more cost effective, with a better return on investment and a more efficient use of natural resources. Because CHP systems utilize heat at the location it is created, it is an ideal distributed generation technology. The following technologies may be configured for CHP operation and are used in a variety of commercial and industrial applications.
Internal combustion engines, also called "reciprocating engines," use a reciprocating motion to move pistons inside cylinders that turn a shaft and produces power. When a cylinder's intake valve opens, the piston is forced down as the top half of the cylinder fills with fuel and air. When the chamber is closed, the piston moves upward as a small spark ignites combustion of the fuel and pushes the piston back down. Internal combustion engines typically range between 5 kW-7 MW and are best suited for load-following applications.
Gas turbines draw in and compress air that is mixed with a steady stream of fuel. The fuel and air mixture is burned to produce hot gas that enters and expands over the turbine’s rotors—making them spin. The spinning motion of the rotors turns a shaft that drives a generator to produce electricity. In CHP systems, the exhaust from the engine is captured in a heat exchanger to generate usable steam or hot water. Gas turbine power plants typically range between 500 kW–25 MW.
Microturbines are essentially small gas turbines. Like gas turbines, microturbines compress air that mixes with fuel and is burned to produce gas, turn a rotor and drive a generator. Microturbine technology is able to achieve very low exhaust emissions. Microturbines typically range from 25 kW-500 kW, and multiple units may be connected together to serve larger loads.
Steam turbines generate electricity from high pressure steam produced in a boiler. Thermal energy is extracted from the steam, used to spin the turbine's blades and drive a rotating shaft and generator. Since steam is produced in a separate boiler, the steam turbine can be powered by a variety of fuels: natural gas, solid waste, coal, woody biomass or agricultural byproducts. Steam turbines are a good fit in industrial facilities where the turbines can generate electricity as a byproduct of excess or waste heat, or where solid or waste fuels are readily available for boiler use. Steam turbines are typically 50 kW to 250 MW.