Arizona, California, and Solar Energy Storage

Lauren Murphy
October 27, 2017

Submitted as coursework for PH240, Stanford University, Fall 2017

What is Solar Energy?

Fig. 1: Solana Generating Station in Arizona. (Source: Wikimedia Commons)

The sun produces a significant amount of energy each day. [1] In fact, the sun produces enough energy in one day to supply all of the energy needs in the World in one hour. [1] Why, then, is solar energy not utilized completely instead of other energy sources? The answer lies in difficulties harnessing and using this energy in an optimal manner.

By the year 2100, there will be approximately 30% more people on Earth than there is today. [1] Because of the increasing population, urbanization and industrialization in our world will also increase. [1] With increasing urbanization and industrialization, the pressure on conventional energy sources is also increasing. [1] This increasing demand makes the world more volatile in terms of energy politics while emphasizing the environmental hazards associated with conventional energy sources. [1] Solar energy is a possible alternative to use of oil, gas, and coal, which are conventional energy sources otherwise known as fossil fuels. [1,2] However, solar energy is still a fledging technology compared to fossil fuels. This is because challenges arise when harvesting energy efficiently and cost effectively. [2]

Overview of Solar Energy in California and Arizona

Innovation and collaboration are needed to face the challenges surrounding solar energy use. California and Arizona have presented great progress in recent years regarding solar incentives. California has strong solar incentive programs and a renewable portfolio standard. [2] Notably, California has strong transmission ties to its surrounding states, including Arizona. Arizona has a large potential for solar energy. [2] Both states are working towards advancing the solar industry through their use of solar energy storage.

Solar Energy Storage

A solar project called Solana, shown in Fig. 1, works on gathering energy in a three-square mile path of desert near Gila Bend in Arizona. [3] It produces 280 MW. [3] Parabolic mirrors focus the sun's energy on black pipes. Heat is then carried to huge tanks of molten salts. [3] This allows the plant to draw heat back out of the salt when the sun sets in order to generate steam and electricity. [3] This is beneficial because it allows energy from the sun to be used even when the sun is unavailable.

The success of Solana has caught the attention of California. The Public Utilities Commission approved a rule that will require California's three big investor-owned utilities to install storage by 2024. [3] Solana is a $2-billion project built with a $1.45 billion loan guarantee from the Department of Energy. [3] The Ivanpah project in California is close behind. It utilizes mirrors mounted on pillars to focus the suns light on a tower with a black tank. It is anticipated that the Ivanpah project will be able to incorporate storage efficiently. [3] Arizona and Californias efforts to create solar energy storage allow solar energy to be more accessible during hours the sun may be inaccessible.

Many companies are investing in these solar facilities to increase opportunities for renewable energy use. Google Inc., a company based in Mountain View, CA, has invested $80 million in six solar facilities in both California and Arizona. [4] Investments in solar energy has allowed for much greater production of solar power. As of 2017, California produced so much solar power during the beginning of the year that it paid Arizona to take excess electricity. [5] This was necessary to ensure California wouldn't overload its power lines. [5] Though California and Arizona have made great advances in solar energy storage, more progress in the solar energy field is needed to increasingly rely on solar energy rather than conventional energy sources.

© Lauren Murphy. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] M. E. Mackay, Solar Energy: An Introduction (Oxford University Press, 2015).

[2] M. Adaramola, ed., Solar Energy: Application, Economics, and Public Perception (Apple Academic Press, 2015).

[3] M. L. Wald, "Arizona Utility Tries Storing Solar Energy for Use in the Dark," New York Times, 17 Oct 13.

[4] S. Li, "Google to Invest in Solar Farms in California and Arizona," Los Angeles Times, 15 Nov 13.

[5] I. Penn, "California Invested Heavily in Solar Power. Now There's So Much That Other States Are Sometimes Paid to Take It," Los Angeles Times, 22 Jun 17.