Environmental Engineering Reference
In-Depth Information
Renewable
power
Green
power
Conventional
power
Lower
Environmental benefit
Higher
Figure 11.7
Green power as a subset of renewable energy that represents renewable resources and
technologies with the highest environmental benefit.
From “Green power market, green power defined,” n.d.
markets. It is important to understand that electricity generated from renewable resources
is “pumped” to the grid and distributed in the same way that energy generated from
nonrenewable sources is, and therefore electricity from renewable and nonrenewable
sources gets “mixed” in the grid becoming undistinguishable. So once in the grid, the fraction
of green power is accounted for by utility companies and sold to customers using some type
of instrument.
The most common way green power is offered to customers is through instruments called
Renewable Energy Certificates (RECs) that represent the environmental attribute of power
produced from low-impact renewable energy projects. These RECs can be purchased by
customers from their local utility company or from green power marketers.
Basically what a consumer pays per kilowatt-hour of green power has two components:
the regular retail price of electricity paid to the local utility company plus a premium paid to
buy RECs that goes back to the company(ies) producing green power. In general, money
collected from selling RECs finance projects that produce green energy. The green power
concept is similar to carbon offsets that was covered in Chapter 7.
One of the problems when buying RECs is having the certainty that those purchased RECs
actually represent green energy generation. To promote transparency, independent certifica-
tion organizations, such as “Green-e” in the United States, certify and verify the authenticity
of renewable energy and greenhouse gases certificates.
On-site generation of “green power”
Industrial opportunities for on-site generation of green power comes from using solar
collection, wind resources, biogas, landfill gas, and biomass. Solar and wind energy are
converted directly into electricity via solar PV panels and windmills. Biogas, landfill gas,
and biomass burned in a boiler produce steam for process heat or it is converted into
electricity with a steam turbine. Biogas and landfill gas can also power a piston engine
attached to a generator to produce electricity. Even when the combustion of biogas, landfill
gas, and biomass generates carbon dioxide, it is considered carbon neutral because it con-
tains biogenic carbon that is part of the natural carbon balance and does not add to atmos-
pheric concentration of carbon dioxide (Intergovernmental Panel on Climate Change
[IPCC], 1997).
Opportunities for on-site generation of power strictly depend on the availability of the
resources. Not all food-processing plants are located in areas exposed to regular winds or to
the proximity of biogas, landfill gas, or biomass.
