The town of Norderstedt puts its faith in district heating when it comes to supplying its population with domestic heating and sees the development of decentralized combined heat and power (CHP) generation as a contribution to the energy revolution. A total of nine modular CHP plants are already in operation. The latest addition to the municipal power plant portfolio is a CHP module supplied by MTU Onsite Energy.
This story begins a good 35 years ago. It is January 1, 1970, when – a few kilometers north of Hamburg – the town of Norderstedt is officially born (see Info box) as an amalgamation of the communities of Friedrichsgabe, Garstedt, Harksheide and Glashütte. What is missing, however, is a geographical connection between the four parts of the town, a true center. In the years that follow, the town's founders draw up plans for the construction of a new district, Norderstedt-Mitte ("central Norderstedt"), which from 1978 are put into effect on the – until then – proverbial greenfield site. Among the developments created over time are around 4,100 centrally located homes accommodating 12,000 residents, all of whom need to be supplied with energy. And right in the middle of them is the Norderstedt municipal utility company, occupying head offices similarly erected in the new town center in 1983. Those responsible take the forward-thinking decision to supply Norderstedt-Mitte with district heating and have what at the time is Germany's largest modular CHP plant installed in the utility company building.
The original engines from that time no longer exist, but there is still a CHP plant in the functional clinker-brick structure in the town center. In the 1980s it became evident that further expansion of the district heating network was no longer economically viable. At the time there was no national energy strategy, while periodically falling oil and gas prices made conventional heating more attractive. It was not until the 1990s that Norderstedt experienced a renaissance in district heating due to an expansion in housing development. And now, in more recent times, the energy revolution has given combined heat and power generation new impetus because, in future, an increasing proportion of electricity has to be generated locally so that carrying energy over large distances can be avoided wherever possible in order to relieve the burden on the grid. At the same time, the price of fossil fuels can be expected to rise because the global oil and gas supply capacity will have reached its maximum in a few years' time. In such times CHP becomes "a universal means of flexible energy generation" according to the latest edition of the Norderstedt Energy Manual. The municipal utility company now has nine CHP plants in operation spread right across the town's administrative area and producing a combined electrical output of 12 MW and a thermal output of almost 12.5 MW. That covers around 20% of the local power consumption.
CHP plant supplies new residential district
Change of scene. A few kilometers from the town center towards the southern end of the Friedrichsgaber Weg. On the eastern side of this street is a small mixed-use trading estate, while on the western side extensive agricultural land and paddocks can be seen. Right here is now a CHP plant made by MTU Onsite Energy. "The big city right next door and the countryside on your doorstep" is how a headline from the brochure "A Center for the Town" puts it. It describes the essence of Norderstedt very succinctly. It takes only 41 minutes on the underground from Norderstedt-Mitte to Hamburg's main railway station, but in spite of the town's location within the metropolitan area, its unusual origins mean that a good proportion of its administrative area still consists of green spaces and open countryside. On one of those previously unused areas in the immediate vicinity of the Friedrichsgaber Weg a new housing estate is currently under construction. The expected energy demand from the new development provoked the municipal utility company to erect a new CHP plant on this site.
The MTU Onsite Energy CHP module is driven by a Series 4000 gas engine and produces nearly 2 MW of electrical energy and a good 2.1 MW of heat at an overall efficiency of 87.9%. "When the electricity prices were higher, we focused more on electricity generation," says Nico Schellmann, Head of Planning at the municipal utility. "But because the electricity prices have fallen, electricity and heat are now equal in value, so high levels of efficiency are important to us." While the electricity generated flows into the national grid so it is impossible to say exactly where it is ultimately used, the heat remains in the local area and supplies the connected homes via a piping system. As the transport of heat over large distances is complex and cost-intensive, the utility company works with local standalone solutions. Each CHP installation serves as a standalone CHP plant that takes care of the heat supply in its immediate surrounding area. The individual piping systems are only interconnected if there are sufficient consumers between the power plants concerned and such an amalgamation is financially viable.
Contribution to energy revolution
"For us, the CHP plants are a good opportunity to create added value here in Norderstedt that goes beyond the normal sale and distribution of energy," explains Schellmann. And goes on to point out its profitability for the municipal utility with the added benefit of long-term customer loyalty. As well as making a substantial contribution to the energy revolution. "We are of the opinion that we have to actively contribute to the transformation of the energy system, and from our point of view the fundamental option available in the urban area is combined heat and power generation." In terms of the energy revolution, the emphasis was still primarily on electricity generation. In Norderstedt, on the other hand, they were generating heat and electricity at the same time, thereby increasing the overall efficiency. Added to that there was the aspect of load-balancing energy – i.e. the reserve generation capacity that the distribution grid operators require for times when demand exceeds supply. "We can use quickly adaptable CHP plants to supplement the volatile renewables, and are already doing so with our facilities," says Schellmann.
Beyond such more universal considerations, the residents of Norderstedt enjoy quite definite benefits from the expansion of the CHP network. They no longer need to keep oil or gas boilers and are provided with an economical "all-round peace-of-mind package". What is more, the supply security is greater because the utility company still keeps conventional boiler systems in reserve in case the worst should happen. By 2020, the local supplier is aiming to have installed a further five CHP plants in the outlying areas of the town, which together with the existing facilities will then provide a combined electrical output of 21 MW and a thermal capacity of just about 21.7 MW accounting for between 25 and 30% of the town's power consumptions. So it is entirely possible that MTU Onsite Energy we be called upon again at some time in the future.