A cool approach to energy storage1 April 2010
Ice Energy has announced plans with municipal utility Glendale Water & Power (GWP) to install 1.5 MW of energy storage on Glendale city buildings and local businesses under a $4.25 million programme. The project is the first phase of a 53 MW storage programme that Ice Energy plans to implement with municipal utilities throughout Southern California, members of the Southern California Public Power Authority (SCPPA). The project will reduce peak electrical demand by shifting as much as 64 GWh of electrical consumption from peak to off-peak periods every year, reducing exposure to costly peak power and improving the reliability of the electrical grid.
The majority of the programme in Glendale is being underwritten through $20 million in federal stimulus funding from the US Department of Energy for GWP’s smart grid project, which includes an advanced metering programme for electricity, in addition to energy storage, to help increase efficiency and reduce energy consumption.
Under the initial phase of the programme, conventional air conditioning units on 28 Glendale city facilities will be replaced with new, higher-efficiency units and paired with Ice Bear energy storage systems to create a hybrid cooling solution that delivers a powerful change in how – and, more importantly, when – energy is consumed for air conditioning. Air conditioning energy demand – typically 40-50% of a building’s electricity use during peak hours in California – will be reduced by as much as 95%.
The Ice Bear energy storage system works with standard commercial air conditioning systems. It operates in two basic modes, ice charging and ice cooling.
During ice charge mode, power is used to freeze water in an insulated tank by pumping refrigerant through a configuration of copper coils within it. The water that surrounds these coils freezes and turns to ice. The condensing unit then turns off, and the ice is stored until cooling is needed.
As daytime temperatures rise, the power consumption of air conditioning rises along with it, pushing the grid to peak demand levels. During this peak window, typically from noon to 6 pm, the Ice Bear unit replaces the energy intensive compressor of the air conditioner.
The Ice Bear unit, fully charged from the night before, switches to ice cooling mode. The Ice Bear uses the ice, rather than the air conditioning unit’s compressor, to cool the hot refrigerant, slowly melting the ice as it travels through a series of copper coils. A small, highly efficient pump pushes ice-cold refrigerant through a modified evaporator coil installed in the conventional air conditioning unit.
The ice cooling cycle lasts for at least 6 hours. Once the ice has fully melted, the Ice Bear transfers the job of cooling back to the building’s air conditioning unit, to provide cooling, as needed, until the next day. During the cool of the night, the ice charge mode is activated and the entire cycle begins again.