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Efficient use of cogenerator heat
2021/03/06 21:41
Efficient use of the thermal energy of the cogeneration module is possible due to the integration of the buffer storage. It should be noted that the buffer storage is not the smallest solution in the energy sector. On the contrary, it takes up a lot of space. But this is its only drawback, because the buffer storage, although the most trivial, but the most efficient method of storing thermal energy

In this article, we will explain why this is the case, what are the benefits of buffer storage and what exactly should be considered when using it in combination with a cogeneration module.

What is buffer storage?

Buffer storage or buffer is the accumulator of thermal energy of the heating system or water heater, filled with water. Its function is to compensate for differences between generated and consumed heat energy. That is, the buffer temporarily stores the generated heat energy so that it can later be used in the form of warm or hot water. The result is improved performance as well as increased efficiency and extended service life of the heating system.

Buffer storages are installed in private houses, as well as in multi-storey microdistricts, large local and regional heat supply networks. They are also used effectively in combination with cogeneration units. Such a system operates in two modes:

the heat generated by the CHP plant is fed to the buffer in case of excess heat energy,
the buffer gives off heat energy when more heat is required than the CHP plant produces.
The specific high and narrow design of the buffer storage ensures good water stratification: cold water is at the bottom, and warm water is at the top of the buffer. Adequate battery insulation prevents heat loss. These characteristics make the buffer storage concept very efficient.

Advantages of a buffer storage combined with a CHP plant

The use of a buffer storage in combination with a CHP plant offers a number of benefits. Buffer:

separates the heat generation from the consumed one, which makes the heat generator more efficient by minimizing the partial load time;
covers the peaks of the heat load and avoids connecting a spare boiler during short-term peaks, which increases the operating time of the CHP;
helps to shift the operating time of a CHP plant to peaks in electricity consumption (for example, from night to day);
prevents intermittent operation of the CHP, which leads to increased wear of the machine;
helps to reduce heating costs due to higher efficiency of the heating system and lower energy consumption;
ensures good integration of renewable energy sources into the heating system;
creates conditions for combining several heat generators into one heating system.
How to determine the buffer size for a cogenerator?

The design of the buffer storage depends on the performance of the cogenerator and the intended approach to its operation. Key criteria include electricity and heat generation, base load metrics, load profiles and process flexibility. The dimensional and volumetric characteristics of the buffer storage are calculated on a case-by-case basis.

How do cogeneration and buffer storage work together?

The cogenerator is equipped with its own circulation pump, with the help of which it draws in the water necessary to cool the engine and exhaust gases at the coldest point of the entire system. After that, the cooling water flows to the heat consumers through the distribution pumps of the heating circuit of the CHPP. The buffer storage takes over the function of a hydraulic switch and allows, depending on the integration, among other things, to disconnect the volumetric flows of the heat generator from the heat distribution system. Depending on the operating state between the buffer tank and the CHP connections, the flows can flow in both directions.

What should be considered when integrating a buffer storage with a cogeneration unit?

First of all, attention is required to select the appropriate buffer sizes, adapted to the operation of the CHP. In addition to this, the integration and control must be coordinated with the overall system, for example a central heating system, since it is important to control when the buffer is loaded with heat and when heat is released.

Another important point is the need for space for placement. Since the buffer storage can sometimes be huge, you need to make sure that there is really enough space in advance to avoid any unpleasant surprises when installing it.