Demand on our power grid continues to rise. Last summer, the East Coast experienced a massive heat wave that set record high temperatures in multiple states and caused over thirty heat-related deaths. Record high temperatures naturally led to increased use of air-conditioning, and a major strain on utilities up and down the Atlantic Coast. The strain became apparent when New York City had power outages and buildings were dimming lights and turning off unnecessary equipment in order to avoid overloading the grid.
A recent Wall Street Journal article pointed to problems already for 2012, and we haven't even entered the hot season yet.
According to the article, "Southern California could be hit with rolling blackouts this summer if reactors at the San Onofre nuclear plant remain shut down for repairs, officials warned this week. The reactors, which normally supply enough electricity to light 1.4 million homes, have been out of service since Jan. 31 after a leak revealed premature aging of vital equipment."
The article continues, "Steve Berberich, chief executive of the organization that manages the electric grid for most of California, said officials are developing a plan to encourage local conservation. But a heat wave still could force officials at his organization, the California Independent System Operator, to instigate rolling blackouts to prevent uncontrolled power outages. Rolling blackouts typically last 15 to 30 minutes at a stretch, spreading the pain."
The concern here is that utilities don't have a plan in place for these types of issues, including extreme heat in the summer months. As the California Independent System Operator looks to devise a plan for conservation, the larger issue of too much demand on a strained grid continues to be the main problem.
Many commercial buildings, which are some of the largest consumers of electricity in the United States, are using over-sized inefficient "just in time" cooling systems. During the summer, most of a building's energy costs are due to air-conditioning during peak daytime hours, when demand and costs are high. Although these over-sized systems have become more efficient, they don't provide viable long term solution to reducing demand on the grid during hot summer months.
The answer to rising demand -- Thermal Energy Storage
An alternative to large just in time cooling systems is to use a hybrid cooling system that includes thermal energy storage. Thermal energy storage (TES) is proven, reliable and the cheapest form of energy storage, yet it is rarely mentioned as part of the energy storage solution. TES tanks store energy in the form of ice, chilled water, hot water or a chemical and water mix. This stored energy can then be used later when the air-conditioning system experiences high demand and or high cost. For example, ice thermal energy storage systems will use electricity during the low demand hours to produce ice, which is stored in tanks. The next day, the stored ice is used to cool the facility when building temperatures rise due to high outdoor temperatures, direct sunlight, occupant body heat and the use of machinery and electronics. The comfort of building occupants is never compromised and relative humidity within the building could be lowered. Meaning the temperature in the building can be higher without the occupants feeling the heat.
Thermal Energy Storage = energy when you need it
We can compare TES to something everyone is familiar with -- hybrid cars. Standard cars have oversized engines for when there is a larger load or a burst of speed is needed for merging and passing on highways. Hybrid cars have smaller engines, which provide greater efficiency and an adequate amount of power. When more power is needed, the stored energy is used to provide the necessary burst of power or the stored energy can be used when traffic is creeping along or at idle for even better efficiency. Commercial cooling with TES is similar. Engineers design cooling systems for peak design days and unanticipated cooling loads. This results in large cooling systems with large supporting infrastructure. Adding storage into these designs allows smaller "cooling system engines" to be used that are more efficient over a wider operating range. When prices are high, or the load is great and a boost is needed, the storage provides capacity. Similarly, when loads are small (at idle or creeping along) the entire cooling load can be supported with low cost stored energy. The connected load is smaller, which is good for everyone, while the safety capacity is provided by storage. The capital for storage comes from installing a smaller electric chiller and support equipment.
TES is beneficial to the environment, too. Utilizing TES reduces the amount of source energy and emissions being released into the atmosphere. A large component of night-time electricity is renewable wind generation. This night-time energy is also more efficiently produced by base-load generation plants. Discharging stored cooling during peak demand hours means utilities don't have to turn on the peaking plants which are usually the oldest and dirtiest utility assets. These peaking plants only come on to meet peak demand mainly caused by air-conditioning.
Not only is TES beneficial to the environment, it saves users money. Grid operators, more and more rely heavily on variable pricing to change consumption to reduce peak demand. As such, demand response revenue opportunities are increasing for users that can shift or change consumption. The price of electricity during daytime hours, when the power grid is reaching maximum capacity, is increased in order to discourage use and relieve stress on the grid. On the other hand, the price of electricity is lower during the nighttime hours when demand on the power grid is at its lowest and supply the greatest. The Edison Electric Institute has said that the only form of energy that has not increased in cost in the last 40 years, when converted to today's dollars, is off-peak electricity. The next logical step for commercial buildings to hedge against price increases and energy pricing volatility is to shift as much energy consumption to off-peak hours when utility demand is lower and rates are less expensive. Shifting cooling off peak can result in a savings of up to 40 percent in cooling costs.
The Smart Grid needs smarter buildings that use disruptive technologies
TES does not diminish the importance of grid energy storage technology, but complements it for greater energy efficiency. The building industry needs to design systems that are able to be better integrated into the Smart Grid. Changes need to be made now in order to help manage our future energy consumption. After all, you can't have a smart grid with dumb buildings.