Latest
Microgeneration Technology for
Houses
Paul Eccleston, 12 Feb 2008,
Telegraph.co.uk http://www.telegraph.co.uk/earth/3325082/Latest-microgeneration-technology-for-houses.html
Energy saving technologies are still in
their infancy and may not provide all the answers needed
to build zero carbon homes.
The warning comes in a new analysis of the
microgeneration technology currently available to
housebuilders.
The UK Government has told the building
industry that all new homes must be carbon neutral by
2016.
With more than 25 per cent of Britain's
energy output going on heat, power and light for homes
housebuilders will be relying on cutting-edge technology
to meet energy-saving targets.
But a joint report from the National House
Building Confederation (NHBC) Foundation and the
Building Research Establishments (BRE) warns there will
be significant risks in using some sustainable
techniques such as solar panels and wind
turbines.
The research assesses the 11 types of
technology available for new developments, including
biomass, solar photovoltaic, air source heat pump and
fuel cell technologies. It examines cost-efficiency and
carbon saving benefits, with crucial factors like
payback periods, seasonal variation, location and local
authority planning requirements taken into account. In
addition the research looks at the capability and costs
of retro-fitting technologies where this is
possible.
The Chief Executive of the NHBC, Imtiaz
Faroohki, said: "This research emphasises the fact that
there is no technological 'magic bullet' to renewable
energy.
"What is made absolutely clear is that
builders need to use the right technology for the right
situation and this needs to be done on a case-by-case
basis, otherwise they are unlikely to deliver on the
three crucial measurements: carbon reduction, cost
effectiveness and customer
satisfaction.
And NHBC Foundation chairman, Nick
Raynsford MP, said: "Leading builders and developers
have stepped up to meet the challenge of creating zero
carbon homes, but much more needs to be done to achieve
real carbon and cost savings for
consumers.
"The report is a first step in helping the
house building industry comprehend the risks and issues
associated with building zero carbon homes. With strict
requirements set out in the Code for Sustainable Homes,
Energy Performance Building Directive and building
regulations, new technologies are crucial to their
success."
"The generation of energy using wind,
water and alternative fuels is still in its infancy for
mass-scale housing developments. The NHBC Foundation is
supporting builders in the complex task of analysing and
selecting the most suitable and cost-effective systems
appropriate to each development to provide a whole
generation of homeowners with efficient and
well-designed housing."
Mark Clare, chief executive of Barratt
Developments, one of Britain's biggest builders, said:
"The NHBC research is an important step forward and it
is clear that much more needs to be done to ensure that
there are reliable and cost effective technologies
available. We are determined to drive the environmental
agenda forward to ensure that the right solutions are
available for our customers."
A Review of Microgeneration and Renewable
Energy Technologies is the most recent in a programme of
sustainability research projects by the NHBC Foundation,
you can download a copy at the
NHBC Foundation website.
Overview
of technologies reviewed in the
research
Biomass systems
In general biomass in the domestic sector
almost always refers to wood fuel, which is only
sustainable if it comes from renewable forest sources.
Biomass systems can have high levels of efficiency,
typically 60-80 pre cent in ranges, pellet stoves, log
stoves and log boilers.
Biomass does require care in installation,
maintenance, siting and also requires a sufficient
amount of space to store the fuel which generally has to
be bought in bulk. In areas which are designated as
smokeless zones not all systems will be suitable,
although modern systems generate considerably less smoke
than their older counterparts.
Key
facts:
Carbon savings: 4.5 Tonnes per year for a three-bedroom
1950s house
Typical
costs of system and installation
(retro-fit): £6,000
Typical
costs of system and installation (new
build): £6,000
Cost
effectiveness - simple payback: N/A
(capital expenditure exceeds savings)
Typical
lifetime: 25 years
Solar photovoltaic
systems
Photovoltaics (PV) work by converting the
sun's energy into electricity using roof-mounted panels.
Cheaper units convert some 5 per cent of solar energy
into electricity and more efficient, and more expensive
units, convert up to 18 per cent of energy received into
electricity.
Power output depends on the type of
materials used in construction and the amount of
sunlight received. The maximum output from PV systems is
in the summer, but the maximum power usage in the home
is in mid-winter. Energy from these systems can be sold
back to the National Grid.
Key
facts:
Lifetime energy, carbon and cost
savings (20-year useful life) per kWp (peak Kw
output): If all electricity is consumed within the
household, the money saved @ 8.5p/kWh is close to
£1,360
Typical
costs of system and installation
(retro-fit): £6,000 per kWp
Typical
costs of system and installation (new
build): £5,000 per kWp
Cost
effectiveness - simple payback:
Currently a system cannot generate sufficient energy
over its lifetime to repay its cost
Typical
lifetime: 25-30 years at rated output,
after which performance deteriorates
Solar hot water
systems
These systems used the sun's energy to
heat water for use in the home for washing and other
domestic uses, they do not usually heat the home itself.
The two standard systems are "flat plate" and "evacuated
tube" and both are normally fitted onto
roofs.
Flat plate systems use a dark plate in an
insulated box to transfer energy into the water system.
Evacuated tube systems are more expensive and
sophisticated, using metal strip collectors in vacuum
tubes but have the advantage that smaller panels are
needed.
In the summer months, these systems can
provide 90 per cent of the hot water needs of a typical
home.
Key
facts:
Lifetime energy, carbon and cost
savings (30-year useful life): Fuel/energy
displaced 60,000-75,000 kWh; CO2 displaced 12 tonnes
(gas) or 30 tonnes (electricity); Gas @ 1.5p p/kWh
around £1,000; Electricity @ 8.5 p/KWh around
£5,700
Typical
costs of system and installation
(retro-fit): £3,000-£7,000
Typical
costs of system and installation (new
build): £1,000-£4,000
Cost
effectiveness - simple payback: Eight to
20 years depending on fuel displaced, conversion
efficiency and fossil fuel/energy price
escalation.
Typical
lifetime: 30 years
Wind power
systems
These work by converting the wind energy
into an electrical output which can be used in the home
after passing through a suitable inverter unit. Care
must be taken in installing these systems to ensure the
home can bear the loads generated by moving turbine
blades.
Obstructions such as trees and other
buildings will reduce the efficiency of these systems
and wind energy is not uniform across the country so not
every region in the country can gain maximum benefits.
The maximum output from wind energy systems is in the
winter, which coincides with the maximum power usage in
the home, but there can be prolonged periods of winter
calms due to high pressure atmospheric
systems.
Energy from these systems can be sold back
to the National Grid and can also generate income under
the Renewable Obligation Certificate (ROC) scheme,
depending on output.
The Renewables Obligation (RO) is the UK's
policy for increasing the contribution of energy from
renewable sources to fulfil the EU Renewables Directive.
The RO requires licensed electricity suppliers to source
a percentage of their sales from eligible renewable
sources.
This percentage increases each year,
starting at 3 per cent in 2003 and reaching 10.4 per
cent by 2010. Each mWh of renewable electricity
generated is accompanied by a Renewables Obligation
Certificate (ROC) and energy purchased from
microgeneration and renewable systems can accrue towards
this whilst, in return, generating an income for
homeowners using renewable
technologies.
Key
facts:
Lifetime energy, carbon and cost
savings (20-year useful life): Electricity
generated 40,000 kWh, CO2 displaced 17,200 kg. If all
the electricity is consumed within the home the money
saved @ 8.5 p/kWh is around £3,400
Typical
costs of system and installation
(free-standing): £3,000 per kW capacity
Typical
costs of system and installation
(building mounted): Typically £1,700 for a 1kW
system
Cost
effectiveness - simple payback: A
well-sited, 50 per cent grant funded 2.5 kW turbine
could provide a simple payback within about15
years.
Typical
lifetime: Up to 20 years with
maintenance and a mid-life overhaul
Ground source heat
pumps
Increasingly popular and in use in
Scandinavian countries in particular in recent years,
these systems work by taking low level retained heat
from the ground and boosting it for use in heating the
home and water for domestic use.
Working in a similar fashion to fridges
these systems are best suited to provide a constant,
lower level, of heating without sharp peaks in
temperature such as is required by under floor heating
systems.
Because of the way in which heat is
extracted, normally through a network of coiled piping,
ground area may be a factor in the ability to install
these systems. These systems are highly efficient,
delivering 300 per cent-400 per cent efficiency against
86 per cent typically seen with condensing gas
boilers.
Key
facts:
Carbon savings: Typically 250 kg per year for a small
two-bedroom dwelling.
Typical
costs of system and installation
(excluding internal heat distribution system):
£6,000
Cost
effectiveness - simple payback: Eight to
15 years
Typical
lifetime: 20-25 years for the heat pump
and up to 50 years for the ground
coils.
Air source heat
pumps
These operate in a similar fashion to
ground source heat pumps but use the ambient air
temperature to generate heat within the home. Unlike
ground energy systems the air temperature input for air
source systems can vary greatly both seasonally and
daily and the systems are not suited to cold winters.
These systems can be highly efficient delivering up to
250 per cent seasonal efficiency.
Key
facts:
Carbon savings: Typically 180 kg per year for a small
two-bedroom dwelling.
Typical
costs of system and installation
(excluding internal heat distribution system):
£6,000
Cost
effectiveness - simple payback: Eight to
15 years
Absorption heat
pumps
Instead of using electricity, absorption
heat pump systems use another heat source such as
natural gas to compress the refrigerant. Otherwise they
are similar in operation to ground or air source heat
pumps.
Key
facts:
Carbon savings: Compared with a condensing gas boiler
operating at 85 per cent seasonal efficiency these
systems would deliver approximately 60 per cent greater
carbon savings.
Typical
costs of system and installation
(excluding internal heat distribution system):
£7,000
Cost
effectiveness - simple payback: Eight to
15 years
Small-scale hydroelectric
systems
These rely on a constant flow of water to
generate electricity using a turbine system. Power
outputs will vary seasonally with flow rates and the
systems may not be suited to all domestic situations
because of the cost of installation against the power
generated.
The capability to generate electricity is
also increased by the size of the vertical distance the
water falls, know as the "head". Greater heads tend to
generate more electricity. Planning issues may mean that
it is not always able to obtain permission to install
hydro-electric plants. The majority of energy created by
these systems is typically sold back to the National
Grid.
Key
facts:
Annual energy, carbon and cost
savings per kW installed capacity (60 per cent
capacity factor): Electricity generated around 5,300 kWh
with 2,300 kg of CO2 displaced.
Typical
costs of system and installation for 100
kW system: Low head - £115,000-£280,000; High head
£85,000-£200,000.
Cost
effectiveness - simple payback: For a
100 kW system operating at 60 per cent capacity capital
costs of around £200,000 with £30,000 in maintenance are
typical. The lifetime yield is around 4,800,000 kWh sold
@ 5p/kWh to the National Grid and with ROC income @ 4.5
p/kWh of around £216,000 would mean an approximate
payback period of 15 years.
Typical
lifetime: 30 years
Micro combined heat and power
systems
This is an emergent technology that is
being suggested as a direct replacement for the boiler
in domestic use. These systems generate electricity as
well as heating the home and providing hot water.
Primarily the systems generate heat, but also
incorporate a heat recovery system combined with
electricity generation, typically using a Stirling
engine system.
Key
facts:
Carbon savings: Carbon savings are as yet not fully
proven under laboratory conditions but suppliers of
systems estimate savings of 1.5 tonnes of CO2 per
dwelling per year with a cost saving of approximately
£150 per dwelling per year.
Typical
costs of system and installation:
Approximately £500 greater than for a condensing gas
boiler
Cost
effectiveness - simple payback:
Estimated at three-five years.
Typical
lifetime: Untested but estimated to be
similar to condensing gas boilers
Renewable combined heat and power
systems
In essence these are exactly the same as
micro combined heat and power (CHP) systems, but they
rely on renewable fuel sources such as biofuels and
biogas. At present the only renewable CHP system
operating in the UK is run on a community rather than
household scale. The potential CO2 savings and the
benefit with regards to addressing fuel poverty may make
these systems an ethically and environmentally
attractive option in the future.
Fuel cells
The chemical energy stored in gaseous
fuels such as hydrogen, methane and propane can be
converted directly into electricity by fuel cell
technology. Although each cell has no moving parts, to
be effective several cells are required, which must be
wired in series, and the resultant generator unit can be
quite complex and incorporate fans, pumps and control
valves.
Efficiencies of more than 80 per cent have
been achieved in experiments with fuel cells, with power
consumption for related equipment such as fans and pumps
being relatively low. However, systems currently on test
only offer 30 per cent efficiency, which means they may
be best suited as CHP systems because of the heat they
generate when operating.
Key
facts:
Lifetime energy, carbon and cost
savings: Not yet available
Typical
costs of system and installation: Prices
of commercially available systems are not yet
available
Cost
effectiveness - simple payback: Unknown
as yet as cost of systems is unavailable at
present.
Typical
lifetime: Projected at 20 years with
some replacement parts required during the
lifetime.
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