Environmental Engineering Reference
In-Depth Information
MW of wind generation at an area known as Goblers Knob East. The charted
load duration curves show:
• Wind energy added to Colorado's generation mix can decrease the
load that must be met with traditional generation.
• Wind in the modeled scenarios does not decrease the generation
needed during peak hours but does decrease the generation needed
during minimum (baseload) hours.
The second conclusion is problematic. At the baseload hours (below 3,000
MW), generation must be shut off or turned down, must be sold outside the
operational area, or will have to be stored. At baseload level, shutting off
or ramping down generation is likely not an option. Selling energy outside
the area during baseload hours may mean giving energy away or even suf-
fering a negative energy price. Storing energy would be a solution if stor-
age capacity is available. The current capacity at Cabin Creek is limited to
about 1,300 MWh and peak power of 300 MWs in an area where wind gen-
eration development is five times greater than the capacity at Cabin Creek.
“Common sense and commercial operations finds that the ability to increase
Cabin Creek load is invaluable in integrating wind during times when wind
generation picks up when load is otherwise low.”
11
It is clear from the foregoing example of integration of wind farms into the
grid in Colorado that large utility scale PHES or CAES can facilitate the addi-
tion of wind energy to a system and enable the addition to contribute to the
baseload. If we assume the extreme case in which there is no wind energy at
peak load, then the capital costs for conventional energy sources to meet the
peak energy demands are incurred, in addition to capital costs for the wind
energy, and the value of the wind farms is limited to reducing fuel costs and
greenhouse gas emissions. With geographical diversity of the wind sources,
the probability of this occurring decreases. The costs for storage systems must
compete with the costs for alternatives such as the addition of gas-fired gener-
ators, demand response, and reducing or disconnecting excess wind power.
The addition of a large number of small solar systems dispersed over the
grid may help optimize the use of storage systems in a different way. A typi-
cal utility network may well evolve from the system shown in Figure 1.6a to
the one shown in Figure 1.6b in which multiple types of storage are indicated
for use in different parts of the system. At present, batteries would appear to
be the most cost effective storage systems to use with small photovoltaic sys-
tems in residences. These might be expected to smooth transient demands
for a few minutes to a few hours. However, at current prices, it would make
little sense to install enough batteries to last for days or longer on systems
connected to a grid.
The relatively short lifetimes and high costs of batteries represent signifi-
cant disadvantages for small stand-alone residential solar systems. The large
amount of ongoing research focusing on batteries means their reliability and
