Environmental Engineering Reference
In-Depth Information
TES systems are installed for two major reasons: lower initial project costs and
lower operating costs. Initial cost may be lower because distribution tempera-
tures are lower and equipment and pipe sizes can be reduced. Operating costs
may be saved due to smaller compressors and pumps along with reduced
time-of-day or peak demand utility costs. The economics of thermal storage
is very specific to a particular site and system. A feasibility study is generally
required to determine the optimum design for a specific application. Several
examples of effective TES installations that cost less than conventional alterna-
tives and also provided significant energy and energy cost reductions exist.
TES projects often profit from unexpected benefits that are secondary to
the primary reason for an action. For example, a well designed TES air con-
ditioning application may experience reduced chiller energy consumption,
lower pump horsepower, smaller pipes, high reliability, better system bal-
ancing and control, and lower maintenance costs.
Peak Shaving
High peak summertime loads make energy costs exceedingly expensive
to consumers and providers. The industry meets these peak loads with
low-efficiency peaking power plants, usually gas turbines, that represent
lower capital costs but higher fuel costs and greater environmental impacts
than arise from other energy sources. A kilowatt hour of electricity con-
sumed at night can be produced at much lower marginal cost than a kilowatt
hour consumed during peak times. Thermal energy storage allows a solar
plant to potentially “shave” peak loads.
Cost to Energy Provider
Energy storage allows a plant operator to maximize profits by manipulat-
ing energy prices, peak shaving, reducing intermittence, and increasing
plant utilization. During periods of low hourly power prices, the operator
can forego generation and dump heat into storage; at times of high prices,
the plant can run at full capacity even without sun. Solar generating capac-
ity with heat storage can make other capacities unnecessary. The ability of
thermal solar plants to use heat energy storage to keep electric output con-
stant: (1) reduces the costs associated with uncertainty surrounding power
production and (2) relieves concerns about electrical interconnection fees,
regulation service charges, and transmission tariffs. Solar plants equipped
with heat storage have the ability to increase overall annual generation by
“spreading” solar radiation to better match plant capacity.
Cost of Storage Implementation
The primary costs for a TES system are the storage material, heat exchangers,
storage tank, and insulation. Washington State University conducted a case
