Geography Reference
In-Depth Information
associated with features such as open flames, gas leaks and high temperatures in
houses. Instead of this within-building heat provision, District Energy schemes gen-
erate heat in some District Centre and provide this via hot water or steam through
insulated pipes to the end consumers, or use it to provide cooling in summer. The
system has many advantages. The district heat generating centre can be based on
many fuel sources and it is scalable, so can be used for small clusters of houses or
large areas in cities. It reduces the problem of intermittency in renewable energy
sources, because excess energy generated by the sun or wind can be converted into
hot water and stored geo-thermally, to be used when demand increases. In addi-
tion, the power is generated locally so the threat of power failures from complex
long distance grids is reduced. Most appealingly the central generating unit is often
based on capturing waste energy from existing power generating systems, although
it can also use the waste energy from large production plants, in what is often called
a co-generation process. Currently most electricity power plants are only a third
efficient, meaning that up to two-thirds of energy from fossil fuel sources is lost,
either in the electricity production process, or through the steam or water cooling
systems, which are major sources of carbon dioxide and other emissions. The heat
energy that would otherwise be wasted is diverted to district heating systems which
can then make these power plants almost 90 % efficient in converting the calorific
fossil fuel input into energy, essentially creating a re-cycling or rather energy-re-
covery approach. Although the district heating schemes have been available for de-
cades, technological changes have increased their effectiveness. The industry now
refers to the latest advances as Fourth Generation District Energy systems. They
have several key features. They allow the use of other sources of energy, such as
from municipal waste incineration or renewable energy. They typically have substa-
tions and heat exchangers to improve heat transfers, as well as smart grids that allow
flexible inputs from various energy sources and two way linkages in the heating
centre, to take in excess power from solar panels etc. Also the use of pre-insulated
supply and return pipes allow the use of lower temperature levels of hot water (EP
2013
). The EU countries, especially in Scandinavia, have the most experience with
this approach, with 270 municipalities in Sweden using the new system. These are
estimated to have reduced carbon dioxide emissions by 60 %, and lowered depen-
dence on fossil fuels in these plants from 80 to 3 % since they have been installed.
In Denmark, Copenhagen now has 90 % of its buildings powered by these schemes,
accounting for 60 % of its heat supply needs, generating 50 % less carbon dioxide
emissions than the old boiler system, saving an estimated 660,000 t of this green-
house gas annually. The plans of Munich's municipal utility company (Stadtwerke
Mnchen
2013
) makes it another progressive city in this context, for it is well on the
way to achieving its goal of being the first city of over a million people to obtain all
its energy needs, of 7.5 billion kwh, from renewable sources by 2025 (SM
2013
).
Although wind and solar energy is being increased, the city gets 4 billion kWh
of waste energy from its power stations in its district heating schemes, saving the
equivalent of 450 million L of heating oil which would have generated 1.1 million t
of carbon dioxide—the same amount generated by all its vehicles in a year. Also
Munich intends to be the first German city to have district heating systems wholly
