Did you know that about 20% of energy in California is used to pump or treat water as compared to the 4% nationwide? That is a huge portion of the state’s total energy use. The reason for this is in California we have to move large quantities of water from a source to the final point of use. Water from the Bay delta is moved 400 miles to San Diego. It has be pumped over two mountains ranges along the way.
The term water energy intensity captures the amount of energy that is used to make/deliver water. For instance, in East Bay MUD water energy intensity is 1.25 MWH per Million Gallons of water (based on 2006 numbers). EBMUD needs to pump water up the Oakland and Berkeley hills and that accounts for a significant portion of the energy use in their water.
The relationship between water and energy has been known and studied for a while (e.g., see the pioneering work of Professor Wilkinson’s on the energy intensity of water), but this information still appears to be largely ignored. There are few if any real bridges between the water and energy industry or professional silos. To better manage energy, you need to understand how the biggest customer, water agencies, are using the energy.
There are four main energy uses in a typical water system:
- Pumps to extract ground water and to deliver water from source to a final point of use.
- Water treatment and distribution with in a service area.
- On-site water pumping, treatment and thermal inputs (heating and cooling).
- Waste water collection and treatment.
EPA offers a top 10 list of ways to manage water. The best way to manage water is to Meter, Measure, and Monitor the water use for each building or facility. This information can help detect leaks and the knowledge of water usage will lead to greater water efficiency.
In commercial buildings, the main user of water & energy are cooling towers. Some use as much as 30K gallons of water per day. Metering the quantity of water put into and discharged from the cooling tower provides information that helps better manage the efficiency of the cooling tower.
Irrigation often accounts for 50% of a facility’s total water use. So minimizing the water used for irrigation will have a significant impact to the overall amount of water used.
According to the Energy Independence and Security Act of 2007, all Federal buildings are required to measure and verify energy and water usage and savings. The list of Best Management Practices is well worth reading.
