Energy storage and the California water crisis
April 21, 2016
The California water crisis has been growing dire for several years now, prompting legislation and community efforts to reduce water usage. Commercial buildings are among the major sources being targeted, as they account for a large portion of overall usage. So much, in fact, that state Governor Jerry Brown has threatened to fine businesses $10,000 for wasteful practices.
Commercial air-conditioning uses large amounts of water - particularly when operating water-cooled chiller plants which employ cooling towers. Fortunately, air-cooled chiller plants can reliably provide cooling on a large scale. When coupled with thermal energy storage, the air-cooled chiller plant can utilize renewable resources, such as wind energy, more effectively, while reducing cooling costs and eliminating the cooling tower, water treatment chemicals and most importantly, its water consumption.
"Air-cooled chiller plants help with water conservancy."
Current water situation in California
It shouldn't come as news that water is quickly becoming a scarce resource in the Golden State. While much of California's efforts to curb water usage has come in the form of limiting agricultural habits, commercial buildings' HVAC systems have been scrutinized as well.
In addition, many utilities use cooling towers in the process of burning fossil fuels. These cooling towers use an immense amount of water to reject waste heat so the energy used to create cooling also contributes to the water scarcity issue. Water is consumed in order to provide comfort cooling for buildings at the source of generation and at the site where cooling is generated.
Controlling water usage in chiller plants
Several options exist to address water usage in large buildings. First, increasing renewable energy consumption can reduce reliance on power plants and their use of water. Second, at the building site, building managers may employ the following options:
- Reduce the cooling load so there is less water needed to reject heat. This can be done by improving the building efficiency, utilizing free cooling and selecting the most energy efficient cooling equipment.
- Retrofit antiquating cooling towers.
- Select an alternative cooling technology such as geothermal and co-generation.
- Installing air-cooled chillers is the simplest approach and would also eliminate water use and have lower first costs.
How does thermal energy storage help?
Thermal energy storage systems can do more with less by reducing the peak demand of cooling systems utilizing a smaller chiller. At night the smaller chiller charges the storage tank with cooling. During the day, the smaller cools the building. When the cooling load becomes larger than the chiller capacity, or a price point occurs, then the stored cooling augments the smaller chillers cooling capability. A partial storage air-cooled chiller system can be similar in peak demand performance to non-storage water-cooled systems while eliminating the cooling system's water consumption.
In California under title 24, the application of thermal energy storage allows commercial buildings to install air-cooled chiller plants larger than 300 tons because doing so eliminates HVAC water usage.
An air-cooled chiller plant with thermal energy storage avoids cooling towers, associated cooling tower costs, chemical costs, maintenance costs and water and sewage costs. Thermal energy storage allows the air-cooled chillers to take advantage of less expensive night-time electric rates. Plus major California utilities also offer incentives for installing thermal energy storage. For example, SCE offers $875 per kW shifted and LA DWP offers $750 per kW shifted. So they're significant cost savings in addition to reduced water usage.
Some may point out that air-cooled chiller plants are less energy efficient than water-cooled plants. With energy efficiency a high priority considering the high costs of energy, is there some balance that may be found to reduce water usage while controlling energy consumption?
Air-cooled plants are less efficient than water-cooled but they have a distinct advantage with thermal energy storage. Besides the dramatic cost savings noted above, thermal energy storage also helps with optimizing the use of renewable energy, which is becoming increasingly important as all commercial building in California must be ZEB certified by 2030, according to Clean Technica.
The future of water efficiency
While energy efficiency is important to national security and the health of our planet, water waste is also threatening to destroy people's lives around the world. From safe drinking water to water-borne diseases, limited water usage is a real problem today, one that requires immediate action in not just California but around the world.
One of the most important ways in combating water waste is by cutting it off at the source. Essentially, stop using water to generate power. At the same time, limit water usage at the building. By switching to a renewable based system, and by cutting down water usage, a global water crisis can be averted - but in order to implement this plan on a massive scale, all forms of energy storage like thermal energy storage must be involved.
