Page 472 - A Comprehensive Guide to Solar Energy Systems

P. 472

Optimal Renewable Energy Systems:

Minimizing the Cost of Intermittent

Sources and Energy Storage

David Timmons
UNIVERSITY OF MASSACHUSETTS BOSTON, BOSTON, MA, UNITED STATES
David.Timmons@umb.edu

25.1 Introduction

Carbon dioxide is a by-product of burning any fossil fuel, and is the main greenhouse gas
responsible for climate change. Controlling climate change will require greatly reducing
fossil fuel use. And regardless of climate change, society will eventually adopt renewable
energy, as fossil fuels have finite availability and are only created over geologic time. Thus
the question is not whether society will adopt renewable energy, but when: carbon-free
renewable energy sources must eventually be used in all global economies. This chap-
ter describes economic principles that should govern renewable energy choices, with a
focus on accommodating renewable energy intermittency. A cost-effectiveness approach
is used, describing the least costly way to achieve up to 100% of energy from intermittent
and dispatchable renewable energy sources plus energy storage.
Electricity is the form of energy produced by the major renewable energy sources,
including solar photovoltaics (PV), wind power, and hydropower, suggesting that electric-
ity will be the predominant form of energy in a renewable energy economy. Electric motors
are also much more efficient than internal combustion engines, and electrification of the
transportation sector will facilitate the transition to renewable energy. Building heating
and cooling can be provided by electric heat pumps, a renewable source of thermal energy
when coupled with a renewable electricity source. Energy in the form of electricity can be
used for most applications (with some exceptions, including jet fuel and shipping fuel).
This chapter thus focuses on electricity supply, though the same principles can be applied
to supplying thermal loads or transportation fuels from renewable sources.
A key characteristic of ambient energy sources including solar and wind energy is that
they are not dispatchable, or not available on demand. Most ambient energy sources have
seasonal as well as daily fluctuations, which vary by energy source and location. Using

467 468 469 470 471 472 473 474 475 476 477