Ida Kiss
possibilities to reduce energy consumption
thus mitigate green house gas emissions?
Carbon
neutral
cities?
H
owever the sustainability of a city
must be understood far beyond
energy efficiency, our approach to a
liveable city is undertaken through
the reduction of energy consumption. Cities
themselves are very energy efficient systems.
That is one of the most important reasons why
contemporary approaches to sustainability
focus on cities as the key to sustainable development on a global level. 1Urbanization has
accelerated in the last decades and especially in
Central-Eastern Europe this process happened
with little control. Urbanization was driven
more by real-estate developers heavily bonded
to political interests. 2This process has lead to
urban sprawl what also meant higher energy
demand of traffic, and majority of the buildings
were built in a poor quality, energy efficiency
was not among the design principles of that
era. Luckily enough global financial crises came
what stopped the heavy growth of building
industry. The age of crisis can be taken as a
possibility for redefining concepts and create
guidelines for a new period of growth.
Charter of Calcutta. 1990. International Conference and
Exhibition on Architecture of Cities. Organised by the
Indian Institute of Architects, West Bengal Chapter.
Reduction of energy consumption is also a
way towards better air quality of our cities.
Nevertheless it has its own limits: we will
always need power to heat the water for a hot
shower, our electrical appliances need to be
charged and we cook. What are the practical
1
World Bank (Carmin, JoAnn; Zhang, Yan) 2009. Achieving Urban Climate Adaptation In Europe And Central Asia
2
While the City of Stockholm voted for fossil
independency in 2003 and became the first
green capital of Europe in 2010 carbon neutrality of Central-Eastern European cities still
seems to be a utopia.
ENERGY FLOW IN CITIES
Energy in cities has its certain flow. Heat and
electricity is generated in power plants and
used in homes, offices, industry and transport. Transport of private vehicles has again
its own energy circuit by directly using fossil
fuels. As a result of our activities a range of
goods and wastes are produced. Waste can
be energy, heat, solid materials and fluids as
well, out if which a certain percentage can be
reused or recycled and other must be handled
with special care as they are harmful to the
environment. The metabolism of a city is
understood by this energy flow3. This system
should be as closed as possible, - meaning the
less dependence on external resources and the
less waste produced – for the city can become
more sustainable.
In the urban metabolism process the various
sectors can be handled as potential energy
sources for each other. Energy cannot just
be consumed but also generated by cars and
buildings. Waste can be handled as an energy
source, though if we reduce the amount
of domestic wastes by more conscious consumer habits and recycling it might threaten
the stability of energy generation by waste
incineration, as it happened in Norway who
already needs to import waste from other
countries. Waste water can also be used for
generating heat and/or electricity in biomass
power plants. There is also a great potential in
generating heat from waste water in-situ with
the help of local heat-exchangers.
Newman, Peter. W. G. 1999. Sustainability and cities :
extending the metabolism model. (Lanscape and Urban
Planning 44 p. 219-226
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Cars can also charge back either locally or for
the bigger network with the help of Vehicle-toGrid system. As cars are parked in 95% percent
of their time on an average they can be used for
storing or generating energy to supply buildings. Buildings can also produce energy by having photovoltaics or wind turbines installed on
them, and the extra can also be charged back to
the system to supply other users.
USE OF RENEWABLE ENERGY SOURCES
IN CITIES
It is more obvious that renewable energy
sources can be used on the countryside,
where there are mostly single family houses
with big roofs, with plenty of space to install
photovoltaic panels or solar collectors. But
renewables can also be used in cities even in
the most densely built areas. Solar panels can
be installed on the roofs though the roof area
per person is much lower in case of multifamily houses and the effective area can even
be much lower as buildings drop shade on
each other. Solar potential should be investigated in detail in case of each city as there
are still great possibilities despite of all these
disadvantages. Multiple terawatts of energy
can be produced in a city like Budapest, as
various researches have already proven it
throughout Germany or the USA.4 In CentralEastern Europe we have better possibilities
to use solar energy than the Scandinavian
countries, and this is not only the lack of
money why it is not widespread in this region but also the lack of knowledge, research
and innovation on the professionals’ side and
mostly because of the scepticism and ignorance of our politicians.
Micro wind-turbines are a reality as well and
can already be seen installed on some urban
buildings. The urban landscape has its own
topography. Bigger streets, rivers and canals
are wind canyons what are advantageous for
these small power-generators.
In the so-called ‘nearby systems’ the produced
energy could be shared within a community
from a commonly realized investment, though
this also requires a mature sense of community
and the legislation of energy-neighbourhoods.
Renewables on the third off-site level of
energy supply are also great alternatives
and can more easily be incorporated to the
conventional system of big energy-suppliers
and small end-users. Besides upgrading the
old power plants for using renewable energy
sources such as biomass or biogas, solar and
wind farms can also feed whole cities.
The use of renewable energy sources in an
urban environment requires an intelligent
energy system, where small producers can
charge back to the grid so that others also can
have a share of the energy they produce.
THE FALSE IMAGE OF GREEN
BUILDINGS
Our cities are made of buildings. 30-40% of the
overall consumed energy is used in buildings;
other 30-40% is used in transport and the
rest in industry. The denser a city is the less
energy is used for transport, and the more it
lives from the business and services sector,
the less is used in the industry. In cities like
New York, London or Berlin buildings are
responsible for about 60% of the total energy
consumed. 5 This fact makes obvious that the
biggest save can be achieved by the energy efficiency of buildings.
Labels as ‘green’ and ‘sustainable’ has value on
the real-estate market. Investors and developers might excel more in green building than
our governments. Especially nowadays their
clients are looking for properties that are
cheaper to maintain than average offices or
the ones built 10-15 years ago. That is why more
and more ‘green offices’ or ‘green buildings’ are
under development recently, however it must
be carefully checked what is there behind this
title. Green building assessment helps to make
a clear difference, although many potential
tenants have no idea about the real meaning of
a certain qualification. Some investors might
then choose the easier way and get the label, no
matter what level the building achieves. Once
the stamp of the assessment is won there will
be no big difference if the building would be an
average or of good performance.
98% of the buildings in our cities are already
built for the next 2-3 decades. There are always
some new developments but the quality of
the overall building mass is depending on the
quality of the old buildings. Buildings need a
renovation approximately every 50 years. By
today prefabricated houses have arrived to the
point where there is an urging need for their
complete refurbishment. 30% of city dwellers
live in this type of houses in Central-Eastern
Europe.6 Prefabs can be refurbished in a very
energy-efficient way with a so called deep-retUNHabitat. (2009). State of the World’s Cities 2008/2009
(p. 280). Earthscan.
5
6
Hegedüs, Jozsef; Teller, Nóra. 2004. 'The social and economic significance of housing management.' In Housing
in South Eastern Europe solving a puzzle of challenges.
World Bank and Council of Europe.
MapDwell project http://en.mapdwell.com/solarsystem/
cambridge
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rofit, when the optimally maximum thickness of heat insulation is applied on their
facades and roofs, windows are changed to
insulating windows with 3-layered glazing and heat-recovery ventilation system is
installed. With the scenario 70-80% of the
energy can be saved annually and the now
energy wasting prefabs can become low or
very low energy demand buildings.7
The level of refurbishment is limited in
case of historical buildings. The core of our
old towns is densely built and many of the
buildings enjoy some kind of protection.
Still, their windows can be renewed to
the level what is comparable to contemporary windows with respect to the original
structure; heat insulation might be applied
on the inner facades and in roofs and the
technology of heat-insulating renderings are
also improving what helps these buildings
to perform better. With a careful estimation
about 40% of energy can be saved in historical districts as well with an 8,5 years return.
Refurbishment should be executed with
strategical thinking in mind as it defines the
energy use of our cities for the next century.
Our cities can really become carbon neutral
if energy efficiency and climate consciousness is the guideline for the fine tuning of
their elements.
Photo: tom chance,wikimedia commons
7
Csoknyai, Tamas. 2007. 'Dunaújváros, Hungary.' Section 3 in
Report for Training for Renovated Energy Efficient Social Housing.
Of course calculating with energy efficiency
only, even thinking about 8,5 years in return,
these interventions bring value on the short
term only. On a long run the whole life-cycle
would be kept in mind and here comes the
value of the energy already built-in in our
existing buildings. This amount of energy
is a clear save, that can also be expressed in
money. The use of environmental friendly
building materials cannot be translated into
saves this easy. However in the whole lifecycle assessment it is shown that considering
the energy that should be used after demolition is much lower in case of these materials
as they are either organic and biodegradable
or recyclable. Building regulations of the
future must require the whole life-cycle assessment and limits for this period of time
should be incorporated.
ZED Factory, BedZED (Beddington Zero Energy
Development) housing development in London, 2003
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