In
densely built residential areas, it is worth generating renewable
energy at local level. A report by VTT shows that this increases energy
efficiency and sustainable housing construction, and leads to the
production of ecological and optimally self-sufficient energy solutions.
Seasonal thermal energy storage (or STES) can markedly reduce emissions
from the heating of localbuildings.
All
new buildings must be close to the level of zero-energy buildings by
late 2020. The related challenges lie in the potential uses of renewable
energy and achieving greater energy efficiency in new construction and
housing. Local production of renewable energy brings considerable
advantages, without placing unreasonable demands on individual
buildings.
VTT's
study presents options for energy generation based on local energy
systems. An analysis of energy needs and production in Vartiosaari,
Helsinki – based on ecologically, socially and culturally sustainable
construction – was drawn up as a case study. A compact city district
will be designed for 5,000-7,000 residents in an area of around 82
hectares. The overall floor area is about 300,000-350,000 square metres.
The results of the study are widely applicable.
Energy
needs and streams were analysed for two sets of building stock,
comparing buildings erected in accordance with the 2012 building
regulations and with the SunZEB construction model (a possible concept
for energy-efficient construction in the future). The analysis suggests
that the calculated heat requirement is only around 50% of the heat
consumption of newer residential areas in Helsinki. A special feature of
the concept lies in the fact that, when being cooled, the buildings act
as a heat source for the heat pump. During cooling in the summer,
renewable energy accumulating in the buildings is recovered and recycled
back into the local district heating network.
The
project studied the impact of introducing solar thermal energy on local
self-sufficiency in heating energy, if excess solar heat in the summer
is stored using BTES (borehole thermal energy storage) or TTES (tank
thermal energy storage) for use in the winter. In both solutions, the
optimal surface area of solar thermal energy collectors was 5% of the
total floor area of the buildings included. Emissions from the heating
of local buildings can be markedly reduced when thermal storage
solutions are used. For example, when using BTES (borehole thermal
energy storage), carbon emissions fall by more than 50% in an area built
in accordance the 2012 regulations and around 40% in a SunZED-type
area. Sulphur dioxide and particulate emissions can be reduced by up to
70% by using TTES (tank thermal energy storage). Self-sufficiency in
electricity for buildings was examined in relation to the number of
photovoltaic panels. The most efficient option when introducing solar
electricity involves meeting 25% of the buildings' electricity needs
using solar panels. This reduces emissions by around 30% in a 2012-level
area and 45% in a SunZED area.
Seasonal
thermal energy storage (STES) of solar energy on a local basis is rare
in Finland, despite demonstrations by international studies that the
utilisation rate of solar energy can exceed 50% of the annual local heat
requirement in similar climate zones. STES also enhances the use of
various kinds of waste heat. The decreasing price trend in renewable
energy is another supporting factor. To increase its energy
self-sufficiency and use of renewable energy, Finland needs to catch up
with the local use of STES by other countries with a similar climate,
such as Sweden, Denmark, Germany and Canada – where district heating is
connected to local STES solutions. This would require e.g. system
development and the piloting of various STES and local energy solutions.
VTT
kicked off its project in April 2015 and completed it in October 2015.
The project was funded by the Housing Finance and Development Centre of
Finland (ARA), Helen Ltd and the Helsinki City Planning Department
(KSV).