The Thermal Energy
Based on efficiency improvements of the past century, prospects are good for achieving efficiency levels that help thermal energy storage realize its promise as a reliable, site-flexible, relatively low-cost option.
22 May 2012 SOLAR TODAY solartoday.org
As renewable energy generation con- tinues its rapid ramp-up — increasing more than 14 percent last year over 2010 in the United States according to the U.S. Energy Information Administration — overcoming the variability of this energy
source will be critical. After all, the wind does not
always blow, and the sun is not always shining.
Several approaches may be applicable to
overcome renewable power variability: balanc-
ing production and demand through forecasting
; aggregating generation from different loca-
tions and renewable sources, e.g., solar, wind,
geothermal and hydropower [ 2]; and, ultimately,
storing electric energy and using it on demand.
This article examines electricity storage methods
that can overcome resource variation and per-
mit baseload power generation from renewable
energy. Thermal energy storage (TES), coupled
to a concentrating solar power (CSP) plant, is
introduced as an option not only for energy stor-
age in CSP, but also as a means for grid storage.
In such a setting, off-peak electricity is stored as
thermal energy and dispatched later to produce
high-value, peak-demand electricity.
Copyright © 2012 by the American Solar Energy Society Inc. All rights reserved.
weighing the storage options
Among the deployed renewable power
sources, hydropower is the most direct in supplying electricity and providing dispatchable power.
However, as shown in figure 1 (page 24),the
hydro energy resource is an order of magnitude
lower than that of wind and solar. Wind technol-
ogy has developed rapidly over the past decade
with its competitive electricity cost, but wind’s
variability does not allow it to provide baseload
power. Although solar heat is the most abundant
renewable source, the cost of capturing it is still
high, and, as with wind, generation variability has
hindered large-scale penetration.
The challenge for energy developers is to
reduce the capital cost of renewable technologies
and improve the energy conversion processes.
Renewable energy’s generation variability and
low energy density make it challenging to collect
and match to demand. Energy storage can bridge
this gap by providing energy continuously and