looking at historical data. We’ve applied
for and received Scottish Environment
Protection Agency licences, we’ve gained
permission from Scottish Water, we’ve
liaised with environmental agencies. We
had environmental impact assessments
done. Positively, everyone’s been in
favour of these works, from the outset
we have made consideration to ensure
that there’s no detrimental effect on
flora and fauna, and everything’s been
done working with the statutory bodies.
“In the long
term there’s
an enormous
amount of heat
that can be
extracted from
such sources –
there’s loads of
conversations
over time, and statutory bodies that will
assess the impact of this.”
RESEARCH
Vital Energi and its partners have
done a good deal of research on
implementation: “We have been to see
various different scenarios and different
projects,” says Lutton. “We went out to
see how it had been done in Drammen in
Norway.” This scheme uses heat pumps
(also from Star Renewable Energy) to
harvest district heat from the waters of
the North Sea.
The temperature of the water from
the Clyde can be between 4°C and 15°C,
while the heat pumps provide an output
at between 75°C and 80°C – the system
is rated at a supply temperature of 75°C,
with the return at 45°C.
The availability of heat from the heat
pumps does not vary with the seasons
as one might expect: “The difference
between summer and winter is really just
an efficiency calculation against the heat
pump inlet temperature,” says Lutton.
“The lower the temperature of water
going in, the lower the efficiency of the
system. The higher the temperature of
water going in, the higher the efficiency.
The system will produce less in the
summer because there’s less demand.
The energy centre is there and available
to take all demand all year.”
The hot water is distributed using
2.5 km of pre-insulated pipe made by
Danish firm Logstor (pictured, above
right). The fully welded stainless steel
pipe is insulated with polyurethane foam,
with an outer casing of high-density
polyethylene and a pair of internal copper
wires for leak detection: “It’s connected
to the site-wide control system and
monitored to ensure integrity of the
distribution network”. The pipes have a
design life of 50 years.
The heat network does not just supply
new-build systems: a number of existing
buildings are included in the scheme,
which typically operate at 82°C/72°C
flow/return temperatures. “New buildings
will be built with 75°C/45°C in mind, but
existing buildings need modification.
It’s basically about the adjustment and
the amendment of control of existing
systems,” says Lutton. By modifying
HVAC – HEAT EXTRACTION
pumps – fitting VSDs to give speed
control – changing from 3-port to 2-port
valves, and adding some control logic,
Vital Energi can lower the flow and
return temperatures in the buildings.
“It’s detailed work,” he adds, “of critical
importance to this type of project – heat
networks need the appropriate building
temperatures”.
Residents need to be brought on
board too: “With anything new there is
change, but a residential customer will be
met with a heat interface unit – it’s very
similar to a combi boiler,” says Lutton.
“It’s not typically a hurdle, but we do
prepare information packs, have briefing
days, and have customer liaison.”
The overall heat network has been
designed to be resilient over the long
term: “Everything is interchangeable.
If a heat pump was to go down in 10
years’ time it’s just a component change
the system doesn’t stop operating. It
can operate forever with appropriate
maintenance.”
10:10 ups the heat
London-based charity 10:10 is
researching and campaigning to harness
renewable energy, including
stored heat from water and
ground sources, as part
of its broader aim to cut
carbon emissions. The
charity focuses on projects
involving commercial and
public sector organisations
rather than individuals, but the
key is community involvement, as 10:10’s
director of campaigns Max Wakefield
(pictured) explains: “Our guiding
philosophy is that we can’t move where
we want to be and as fast as we need to
get there unless everybody is involved.
You end up with something where
everybody feels they are contributing.”
The ‘Solar Schools’ project ran from
2010-15 and involved 80-90 schools.
Wakefield says that a school works well
both in terms of local involvement
and also technical feasibility.
The charity’s ‘Lost Rivers’
project, meanwhile, explored
the possibility of extracting
heat from the underground
rivers flowing beneath London
– including a suggestion of installing
heat pumps in the Tyburn to supply
nearby Buckingham Palace. One of
10:10’s current projects is ‘Powering
Parks’, a partnership with Scene
Consulting and Hackney Council that will
demonstrate the benefits of groundsource
heat pumps in green spaces to
heat on-site or nearby buildings.
May 2019 www.operationsengineer.org.uk 25
/www.operationsengineer.org.uk