Peak load reduction with cogeneration plant

April 15, 2020

Fraunhofer IISB has integrated a new cogeneration plant into its operating infrastructure. A special operating strategy was used to optimize the plant for peak load reduction.

© Kurt Fuchs / Fraunhofer IISB
In the basement of Fraunhofer IISB: Cogeneration plant and thermal storage.
© Fraunhofer IISB
Series of measurements of a peak load reduction carried out at Fraunhofer IISB: With a maximum permissible reference power of 700 kW, the peak load could be reduced by approx. 20 %.

In a combined heat and power unit (CHP), a  generator is operated by a combustion engine.  In order to maximize overall efficiency,  the thermal energy generated is also used  for heat supply. This makes cogeneration  units suitable for heating private homes as  well as for supplying electrical and thermal  energy to energy-intensive industries.

Thermal energy storage systems optimize  the running time

The new cogeneration plant at the  Fraunhofer Institute for Integrated Systems  and Device Technology IISB has also been  expanded to include a thermal energy storage  system. This allows the CHP unit to be  operated largely independently of the current  heat demand and thus more flexibly in  terms of time. This maximizes the annual  operating time and accelerates the cost  compensation of the plant.

Peak shaving reduces electricity costs

With a specially developed operating strategy  for the cogeneration plant, which contains  a finite state machine, the peak loads of the institute could be reduced by 20 %.  Peak loads are temporary sharp increases in  electricity consumption that often cause  high energy costs. The reduction of peak  loads (peak shaving) therefore allows to  lower the resulting electrical energy costs.

Within the operating strategy, a predefined  part of the capacity of the heat storage is  reserved to enable the system to operate  even when there is a high demand on electricity  but a low heat demand. An additionally  integrated battery system bridges the  start-up time of the power plant from  standby to full operation, supports the CHP  during high peaks and shaves small peaks  single-handedly.

The system is well suited for heat and  power supply of medium-sized companies;  the Fraunhofer IISB itself serves as a demonstration  platform. Specially developed algorithms  optimize the individual dimensioning  of parameters of the CHP system and  its components (e.g., electrical and thermal  power, capacity of energy storage) and estimate  the potential savings.