PowerStor® is a Combustion Turbine Inlet Air Cooling (CTIAC) system that offers one of the highest net output of any CTIAC application. The large increase in power output (20-25%) is due to the low auxiliary power consumption of the system during on-peak operations.

Thermal Energy Storage (TES) systems utilizing ice or water, in the simplest of terms, are capacity reserves. Inside every ten foot cube of ice is more than 3.5 MWh’s of generation capacity that would otherwise be lost to combustion turbine performance decreases during high ambient temperature conditions. Low cost off-peak power is used to build the cold reserve, and the cold reserve is used to cool the inlet air to the turbine(s) during on-peak periods to increase power output.

The high energy density of ice, due to its latent heat of fusion, makes it an ideal medium for thermal energy storage and substantially reduces the size of the insulated storage tank. The main components of the systems are:

  • Cooling coils in the CT inlet structure
  • Refrigeration system including evaporative condensers
  • Insulated Thermal Energy Storage Tank(s)
  • Evaporators or “Ice machines” on the top of the tank
  • Controls
  • Interconnecting piping

With ice harvesting systems, during on-peak periods, 32-33°F water is taken from the bottom of the tank, circulated through the cooling coils and sprayed back onto the ice pile in the tank in an even manner. Off -peak, water is taken from the bottom of the tank and pumped up to the plate ice machines on the top of the tank. At the same time, refrigerant is also pumped to the plate ice machines where is freezes the water into sheets of ice. A hot defrost cycle is timed to warm the plates and the ice slips off back into the tank. Ice based systems are ideal for peaking capacity times of less than 8 hours.

Conventional chillers are a more cost effective design for peaking capacities of eight hours or more. With conventional chillers, chilled water is produced during off peak times and is pumped into the bottom of a thermal energy storage tank while warm water is removed from the top of the tank and sent through the chiller. During peak times, chilled water is pulled from the bottom of the tank and sent to cooling coils in front of the turbines(s) to cool the air and warm water is returned from the cooling coils to the top of the storage tank.

From the perspective of a power plant owner, TES systems offer a number of energy and capacity electric sales options. The flexibility of TES systems is different than combustion turbines. An example of this is a base load combined cycle plant that can have a separate power sales contract for peak capacity by the addition of a PowerStor® system. Another capability is continuously burning ice for three days straight when power sales prices are at their maximum. Let Caldwell Energy show you how flexible PowerStor® systems can enhance supply side management and plant profitability.