Drought and Energy – An Interesting Water/Energy Nexus

Published: Mon 14 Jul 2014
A blog entry by Christine Hertzog

Contributed by:

Christine Hertzog
Managing Director
Smart Grid Library

Christine Hertzog's Blog

The water/energy nexus and the ramifications of this closely intertwined relationship, particularly with energy generation, needs to gain awareness beyond policy wonks in the western states of the USA. These previous blogs about California’s water issues and the water/energy nexus provide good background about climate change impacts to water and energy.

If we look at water as a supply chain, it is easy to spot the similarities to the traditional electricity supply chain, which consists of generation, transmission, distribution, and consumption. The water supply chain is comprised of water sources (similar to generation), transport (similar to transmission), treatment (similar to distribution) and consumption.  The Smart Grid is transforming the electricity supply chain into a value chain in which consumers can also become electricity producers or prosumers.  The Smart Grid will also play many vital roles in the connections between energy and water.

There are serious problems at every stage of the water supply chain starting with sources.  Water sources can be grouped in three categories:  1) precipitation in the form of rain or snow; 2) groundwater sources such as rivers, streams, and underground aquifers (all rely on precipitation for resupply); and 3) conversion of briny and brackish water into water suitable for plant or animal (including human) consumption.

The current news focus in California has been on possible delay of once through cooling rules to address the unexpected closure of a nuclear power plant in southern California due to safety concerns.  Once through cooling is a technique that uses water drawn from older coastal and bayside power plants in the electricity generation process.  It is extremely destructive to marine environments.   Seawater intake – up to 16 billion gallons per day - is expelled at high temperatures.  Both intake and outflow are harmful to the aquatic life, which confronts many other challenges caused by climate change, environmental pollution, and overfishing.    New power plants are designed to use air instead of water, eliminating this environmental peril, and many older plants in California are in the process of retooling or retirement.

Northern California, which includes the San Francisco Bay Area, has different power concerns that are caused by climate change and the current drought, which is labeled extreme to exceptional for most of the area.  The California Energy Commission (CEC) notes that between 8 to 17%

of in?state generation comes from hydropower.  Approximately 75% of this in-state hydropower is produced by 150 high elevation hydroelectric plants situated in the Sierra Nevada and Cascade mountain ranges.  The supply reservoirs for these plants typically contain less than a year’s storage capacity.  Most rely on snowpack for water storage.

Snowpack is perfect time-release water storage when it is available.  However, every climate change model forecasts that most of the west will receive less precipitation in the coming decades.  That precipitation that does occur is increasingly likely to be rainfall instead of snow.  We are facing a future in which these hydro plants have lost their predictability for use.  If a hydropower plant operator releases water now to generate electricity, there’s no certainty that there will be sufficient annual precipitation to resupply that reservoir for future generation, or that it will be conveniently time-released in melting snowpack.

Demand response (DR) is a tactic that utilities use to reduce peak electricity use.  In California, most utilities have summer peaks that correspond to very hot weather and the need for electricity to power air conditioning across a region.  These utilities have DR programs that induce residential, commercial, industrial, and agricultural customers to voluntarily cut back their consumption during the hottest days.  We can all connect the dots to realize that there will be a greater need for DR programs and participants as all regions of the USA will experience higher temperatures due to climate change.  But when you connect these dots, you also realize that regions and utilities that are reliant on hydropower will have to leverage more demand response (DR) to conserve water in hydropower plants that are at risk of limited resupply – particularly if that resupply comes from snowpack.

Demand response for water conservation - it’s one aspect of the water/energy nexus that has received little attention, but it will certainly play a larger role in western states that rely on hydropower in the future.   Electricity prosumers, producing predictable negawatts to offset peak demand, will play a critical role in this particular intertwining of water and energy.  As important as DR will be, its only part of the energy supply solution as overall temperature rises are predicted from climate change.  Western states will have to rely on more distributed generation from other clean, renewable energy sources to compensate for losses from hydropower as its predictability of supply and timing are disrupted by climate change.  Smart Grid technologies can certainly help integrate renewables and other distributed energy resources as a creative response to conserve water and manage the intricacies of the water/energy nexus.

Christine Hertzog
Smart Grid Library