ADVANTAGES AND SYNERGIES
There are significant advantages that often proceed from employing DC and/or TES. And there are often meaningful synergies when integrating DC and/or TES with CHP or on-site power generation.
Seasonably variable thermal loads can be combined to achieve a relatively constant demand for thermal output year-round
District cooling versus individual chiller systems
The advantages of DC include economies of scale, higher energy efficiencies, greater labour efficiencies, concentrated and reduced maintenance, better ability to provide desired extra thermal back-up, better ability to provide sophisticated controls and operator training, overall space savings, and very significantly, a better ability to incorporate complementary technologies for economic benefit, such as TES, hybrid chiller plants, integrated heating and cooling, and combined cooling, heat and power (CCHP).
Thermal energy storage
The advantages of TES used in large cooling systems, such as DC, include management of peak cooling demand, reduction of peak electric power demand (and its associated) cost, capturing savings from time-of-day or real-time energy rates, reduction in the amount of required installed chiller capacity (and its associated cost) often achieving a net capital cost savings, and enhanced redundancy and/or emergency reserve cooling capacity. The secondary benefits include dual-use of TES as fire-protection water storage, or the enhancement of cooling distribution by siting TES at a satellite location remote from the chiller plant. Integrating DC with CHP When integrating DC with CHP, beneficial synergies ensue. Seasonably variable weather-dependent thermal loads for heating and cooling can be combined to achieve a relatively constant demand for thermal output year-round. Thermal revenues are spread more evenly throughout the year. On-site power generation can more easily be matched to a useful thermal output year round, and thus can often be more readily justified economically. Also, the cooling system can be used to provide turbine inlet cooling for any gas turbines that may be employed in the on-site generation system, thus dramatically enhancing the hot weather power output of the combustion turbines, typically by 20%–30% or more.
Integrating TES with CHP and on-site power
When integrating TES with CHP or other on-site generation, beneficial synergies also result. Daily variable demands on electricity and cooling can be balanced to achieve a relatively constant demand for power and thermal output around-the-clock. TES can reduce installed chiller plant capacity and often reduce net capital cost. Once again, on-site power generation can more easily be matched to a useful thermal output around-the-clock, and thus can often be more readily justified economically.
Denmark-based district heating company Danfoss has acquired 100% of the shares of Austria’s Nopro Wärmesysteme, which markets substations and automatic controls for biomass-based district heating systems. The company has 35 employees and a turnover in 2005 of approximately €5 million.