Combined Heat and Power plants (CHP units) are remarkably efficient power generators because they produce electrical power and heating simultaneously. This makes them ideal for the decentralised supply of power to buildings of all kinds, including industrial plants and companies that wish to generate their own power independently of the public grid.
Which is why Kraftanlagen has specialised in the planning, construction, maintenance and modernisation of power plants, including large ones, all based on the CHP principle. Furthermore, the energy concept of municipal utilities enables domestic households to be supplied as well.
An extensive and complex refurbishment project is now approaching successful completion at the Stonsdorf site operated by Stadtwerke Norderstedt. Stadtwerke has commissioned a full CHP update using the very latest technology for a plant constructed 13 years ago by Kraftanlagen that has been connected to the town’s public grid since that time. As part of its modernisation efforts, Stadtwerke Norderstedt is having its CHP sites renovated. This with the aim of making the operation of its plants more efficient and also more CO2-neutral in future.
CHP in Stonsdorf now more efficient with heat pump
In 2011, Kraftanlagen built a single-storey gas engine plant at this site, with an electrical output of 2 MW. The conversion concept included extending the building by a further storey. This technical expansion comprises two heat pumps that boost the efficiency rating of the entire plant during CHP operation. This is made possible by using the exhaust gas emissions from the gas engine to cool it down to 20 degrees. Before this, it only got cooled down to 70 degrees. In approximate terms, this results in an additional 500 kW of thermal power being available to the heat pump system. In this way, through the use of electrical power, the heat pumps are able to supply an additional 800 kW of power to the district heating system.
Significantly higher efficiency achieved by heat pump and convection cooling
At the same time, yet another source gets utilised for the heat pump system.
The room air heated by the radiant heat from the unit is channelled through a recirculating air cooling coil on the upper storey of the building. This is then cooled and gets directed back into the unit room. In this way, the radiated heat from the unit becomes usable heat. It also gets fed by the heat pump into Stadtwerke’s district heating network. In the unit room, only the combustion air is fed in as supply air.
‘Standalone operation’ is possible with a heat pump
However, that’s not all: when the CHP system is not running, the heat pump system operates in standalone mode, using an air cooler system located on the roof of the building as a heat source. This enables Stadtwerke to supply its connected households with district heating – entirely from renewable sources – at a flow temperature of up to 80 degrees even without operating the gas engine.
Technical data of the CHP in Stonsdorf, Norderstedt
Martin Heimann, Head of Sales for Decentralized Energy Systems at Kraftanlagen Energies & Services SE, and Steffen Blohm, Presetter at Kraftanlagen Energies & Services SE, at the Stonsdorf CHP plant
© Cyril Abad
Previously, with similarly extensive conversion measures, Kraftanlagen had modernised the CHP systems operated by Norderstedt Stadtwerke at its Buchenweg and Nord sites. Taking the Buchenweg site as an example, a heat pump is supplied from the engine exhaust gas. This has increased the overall efficiency rating of the CHP plant (here too) to 106 per cent (thermal: 68.9 percent, electrical: 37.6 percent). Here too, measures were taken to achieve two objectives. These were to increase efficiency while at the same time reducing CO2emissions. The town of Norderstedt is pursuing ambitious targets, in relation to both the ‘electricity transition’ and the ‘heating transition’. The town now operates three CHP plants and refurbishment of these is a key element in achieving these targets: the addition of heat pumps has increased the efficiency ratings at all three locations.
In the long term, these refurbishment measures will help to achieve output compliant with a 1.5-degree target through a focus on the generation of CO2-neutral electricity coupled with the use of renewable substitutes for natural gas.
A digression – Why CHP plants are an important pillar of CO2 reduction and why they constitute such important factors in relation to the goal of energy transition
The goal of energy transition requires modernisation on a huge scale of the existing combined heat and power plants. Across the board, less efficient heating systems powered by fossil fuels need to be replaced by smarter systems. Combined heat and power plants have a crucial role to play in decentralised energy concepts of this kind. Because these plants generate electricity and heat simultaneously, based on the principle of combined heat and power generation, they have high efficiency ratings of up to 97 percent (compared to between 80 and 90 perfect for conventional CHP plants). In particular, CHPs that run on non-fossil and renewable fuels make a significant contribution to reducing CO2 emissions. CHPs can help to avoid transmission losses and can stabilise public electricity grids by directing electrical power and heat into public electricity grids and heating networks. In addition, through their decentralised generation of power, they also help to stabilise the electrical power grid, especially during peak times. Furthermore, if those CHPs are operated with non-fossil and renewable fuels, they enable greater integration of renewable energies into the energy supply system.
CHP types based on different technical solutions and dimensions
- The most widespread are (still) what are referred to as engine CHPs, in which conventional petrol engines are used to operate a generator that in turn produces heat and power.
- Instead of an engine, the CHP plant is driven by a gas turbine. The disadvantage of these CHP systems is that they produce less power (electricity) but they are more effective at generating heat.
- The principle of the steam turbine CHP is based on the steam generated during combustion. This steam is then used to drive a very powerful turbine.
- If required, the Stirling engine CHP can also be operated with pellets or wood chips. Although the efficiency rating of the Stirling engine concept is not that great, it does help to reduce CO2 levels, provided it is not operated with gas.
- Fuel cell CHPs are not yet in widespread use. Here, heat and power are produced by triggering an electrochemical reaction, e.g. by using hydrogen as fuel. This concept has a climate-neutral ecological footprint.
- Nano-CHPs are systems that generate less than 2.5 kW of power and less than 12 kW of heat. They are most frequently used in smaller residential buildings.
- A micro-CHP is one with a maximum power generation of 15 kW and a maximum thermal output of 30 kW. These are a popular choice for small businesses or multiple-occupancy residential buildings.
- The mini-CHP variant is defined by the generation of up to 50 kW of electrical power and 100 KW of heating. Large residential buildings and medium-sized companies are the most frequent users of this type.
- With output data in the MW range, these are the kind of (large) CHP units commonly used by municipal utilities or industrial companies.
Martin Heimann, Head of Sales Decentralized Energy Systems at Kraftanlagen Energies & Services SE, on the roof of the CHP plant in Stonsdorf
© Cyril Abad
Why decentralized energy supply is so important for climate change
Kraftanlagen is the specialist for decentralized energy supply concepts. Decentralized energy supply essentially means that electricity and energy are produced in a CHP unit, for example, exactly where they are needed. CHP units are based on the principle of combined heat and power generation. Combined heat and power generation is the conversion of energy from a combustion process into mechanical or electrical energy with the simultaneous provision of usable thermal energy in one process. The heat produced in parallel to the electricity generation is used for heating and hot water or for production processes. Thanks to the CHP principle, the fuels used are used multiple times to generate energy with high levels of efficiency, ideally while minimizing CO2 emissions at the same time. A conventional CHP unit generates electricity by means of a combustion engine, during the operation of which the resulting waste heat is used, for example, to feed a district heating network.
Decentralised energy management
By way of example, if households obtain their heat and power from a CHP operated by their municipal supplier, this delivers a major benefit in terms of the ecological balance of their local region. This requires closed distribution grids and a decentralised energy supply. One based on renewable energies that is integrated into a decentralised energy management system. Ideally, the most important components of a CHP are engines that run on renewable fuels instead of on fossil fuels such as gas or oil. Another aspect of decentralised energy management can involve the use of ‘virtual power plants’. These combine the output of plants operated by different, decentralised energy producers. Kraftanlagen is a specialist in the planning, building and maintaining of this kind of complex system.
The components of a contemporary system for decentralised power generation:
- Combined heat and power plant
- Gas turbines
- Combined heat and power system
- Internal combustion engines
- Heat accumulators
- Heat exchangers
- Heat pumps
Kraftanlagen is your development partner for decentralised energy supply concepts, or for decentralised power supplies, serving systems from 1 MW. We are able to plan and design your decentralised system, creating precisely the combination of components that will enable you to achieve your goals safely while also making an active contribution to climate change, and of course providing a secure supply of heat and power.
