Environmental Engineering Reference
In-Depth Information
% when run
as pumps. Of course, the pump power has to be supplied
from other sources.
You do not need a large river to generate large amounts
of power for part of the time. All you need is a big enough
lake and a water supply that can make up for losses. This
makes sense where daytime power costs more than night-
time power so that the supplier can make a pro
% for generation and can be as high as
tby
playing off the difference; generating electricity in the
daytime and pumping at night. As far as greenhouse gas
emissions are concerned, they depend on those of the
emissions of the power source used to pump the water
uphill. Solar power does not make much economic sense
for this since it is generated during the day when electri-
city prices are high. It does not make sense to use high-
priced daytime power to pump water uphill to generate
power at night when prices are low.
There is little new to say about hydropower. The tech-
nology is mature and its use will be determined by choices
made in many different places. Costs for large-scale
hydropower are at grid parity or below, and as far as
greenhouse gases are concerned, it is a winner.
.
Ocean Energy
In
Chapter
the total energy in all the world
'
s waves
and all the world
s tides was estimated to be about four
times the TPES. Of course only a tiny fraction of that is
really accessible. The tidal lift or waves or the tempera-
ture difference between surface and deep waters in
mid-ocean are no use to us because we cannot yet
manage to get the energy harvested back to the shore.
'
