Economic Efficiency of Trigeneration

The profitability of an investment plays an important role in the decision-making of investors. As for cooling systems, investors can choose between either conventional compression cooling systems driven by electricity or thermally driven chillers. In many cases, investors decide for an electric compression system, which is technically less advanced. As a result, it is easier to calculate the economic efficiency in order to receive a basis for the investment decision. The consideration of the following advantages of thermally driven cooling systems however is more complex. 

  • Economic consideration of the integration of existing heat and waste heat
  • Special conditions for the provision of heat during summer
  • Reduction of the cost-intensive peak times of electricity demand with trigeneration in contrast to the electric compression cooling system
  • Harmonization of the electricity usage during the year
  • Consideration of the possibilities of cooling storages with trigeneration systems

An important key factor for the economic usage of trigeneration is the supply of heat at low costs. If heat, for the cooling via trigeneration cannot be provided at low costs, the cooling with conventional electric compression cooling systems offers an economic efficient alternative. Every decision on the way of cooling is therefore a special case which has to be considered separately under the unique local conditions. The required heat for the cooling via trigeneration can be provided by different sources as:

  • Waste heat from cogeneration plants
  • Waste heat from industry
  • Local and district heat

The decision for cooling from heat via thermally driven chillers provides the advantage that consistent heat provision can be achieved in summer. This might be relevant for combined heat and power plants e.g. cogeneration units and district heat providers, which should produce electricity in summer.

Source: Henning Hans-Martin, Urbaneck Thorsten, Morgenstern Alexander, Nunez Thomas, Wiemken, Edo, Thümmler, Egbert, Uhlig, Ulf (2015) Kühlen und Klimatisieren mit Wärme. Bine-Fachbuch.

Consistent capacity utilization of heat generation via trigeneration in the course of the year during summer:

The graph indicates that the normally high demand of cooling during summer can be covered via the free capacities of heat generation. An additional integration of heat from solar power could be beneficial if there is high cooling demand and solar radiation and cooling demand are both high at the same time. Therefore, various possibilities of the analysis of economic efficiency exist. 

Schematischer Wärme- und Kältebedarf im Jahresverlauf; Quelle: Eigene Darstellung Technische Hochschule Nürnberg Georg Simon Ohm

Figure 2: Heat and Cooling demand