170038 4G Heat Networks - sav-systems.com · Strategic review of 4G Heat Networks in the UK 2...

www.sav-systems.comRev: 1.0 04/2018

Strategic review of 4G Heat Networks in the UK


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Published in January 2018, the ADE’s ‘Heat Networks in the UK’ report highlights the contribution of heat networks to the UK’s energy and carbon reduction requirements and the opportunities to transform the way we heat our homes and buildings.

There is an increasing awareness of the signifi cant benefi ts for the UK from wider use of well-designed heat networks. SAV therefore actively supports development of sustainable buildings that focus on long life operation and performance, making optimum use of renewable energy sources - and which can be future proofed in line with 4th Generation (4G) heat network design philosophy.

SAV is committed to improving the indoor environment whilst using the minimum amount of energy.

Optimum indoor climate, minimum energy usage

Reference: 4th Generation District Heating (4GDH)Integrating smart thermal grids into future sustainable energy systems

http://dx.doi.org/10.1016/j.energy.2014.02.089


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Contents

Introduction .............................................................................4

Heat networks – a brief history .............................................4

Why we need 4G Heat Networks ...........................................5

Growth of renewable energy sources ...............................................5

Growing complexity of energy networks ..........................................5

Planning for energy storage .............................................................6

Low temperature operation .............................................................7

Building design ................................................................................8

Measure to manage.......................................................................10

Exploiting waste heat opportunities ...................................10

Making 4G Heat Networks a reality ....................................11

Does scale matter in heat networks? ..................................12

Block heating: West Bridge Mill .....................................................12

Multiple block heating evolving to district heating: Aberdeen Heat & Power ................................................................13

District heating: Fredericia, Denmark ..................................13

Summary ................................................................................14

References .............................................................................15


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IntroductionIt is now well accepted that heat networks are a key element in the UK’s commitment to reducing carbon

emissions. In September 2017 the Department for Business, Energy and Industrial Strategy (BEIS) stated:

“Heat networks form an important part of our plan

to reduce carbon and cut heating bills for customers

(domestic and commercial). They are one of the most

cost-effective ways of reducing carbon emissions from

heating, and their effi ciency and carbon-saving potential

increases as they grow and connect to each other.”

While 47% of the UK energy use goes to heating, the Committee on Climate Change has estimated that

around 18% of UK heat will need to come from heat networks by 2050 if the UK is to meet its carbon targets

cost effectively. Yet currently, BSRIA estimates that only around 2% of the UK’s heat demand is covered by

heat networks – compared to around 13% for mainland Europe.

The heat network consumer survey by BEIS (Dec 2017) suggests that heat network consumers, on average,

pay around £100 a year less for their heating and hot water, compared to non-network consumers, which

can be even larger with better design and operation of heat networks.

However, for heat networks to fulfi l their full potential during the low carbon transition it has become clear

that a sustainable approach is required to their design and operation. In particular, the new generation of

heat networks that integrate electricity, thermal and gas grids needs to be adopted to enable the wider

use of renewable energy.

Crucially, this 4th generation of heat networks (4G) needs to adopt an ‘open source’ approach to heat

sources, with the inherent fl exibility to exploit the best heat and power sources available – both now

and into the future.

Heat networks – a brief historyHeat networks (aka district heating systems) have been used for over 100 years around the world, gradually

improving in effi ciency through each generation.

The 1st generation of heat networks,

in the late 19th Century, distributed

heat in the form of steam. These were

superseded in Europe in the 1920s

by networks using water at around

100°C (2nd generation) and then in

the mid-20th Century by sub-100°C

networks (3rd generation).

Most of the heat networks operating in the UK today are of a 3rd generation design and, compared to

2G networks, feature a number of improvements. These include improved pipe insulation, wider use of

pre-fabrication and more effi cient energy production from a decentralised energy centre. They have also

introduced system metering as a fi rst attempt towards digitalisation.

“Heat networks form an important part of our plan

to reduce carbon and cut heating bills for customers

(domestic and commercial). They are one of the most

cost-effective ways of reducing carbon emissions from

heating, and their effi ciency and carbon-saving potential

increases as they grow and connect to each other.”


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However, the design of 3G systems creates an issue for the increased uptake of renewable and low carbon

energy sources in the future as it ‘ties’ them to the heat sources they were originally planned to use. Typically,

this would be an energy centre powered by Combined Heat and Power engine backed by boilers.. While

there may be an opportunity to add lower carbon energy sources in the future, this would require extensive

upgrading of the energy centre and the buildings being served by the network.

Thus, a traditional 3G heat network is far from a sustainable solution. It is rather like an isolated island

community that is only concerned with its own issues with no consideration of wider global issues. As such,

3G design does not address the rapidly changing energy landscape and in particular, the growing use of

wind power in the UK.

Why we need 4G Heat NetworksIn developing new heat networks, it may be tempting to follow the path of least resistance and simply

roll out more schemes based on the 3G design criteria. However, this will fail to address the challenges

and opportunities that lie ahead, particularly in relation to the growing production of intermittent

renewable energy.

A key characteristic of 4G design is that it incorporates the wherewithal to manage the increasing complexity

of energy networks, and the intermittent availability of ‘green electricity’, effi ciently and cost-effectively.

Growth of renewable energy sources

Nearly a third (29.8%) of all UK electricity in the second quarter of 2017 came from renewable sources,

most of it from wind. Onshore wind generation increased by 50% in 2017, while offshore wind energy

rose by 22%.

This is just the beginning. The UK already has the largest offshore wind capacity in the world and this is

set to increase production rapidly thanks to a £320m investment pot made available by the UK government.

A number of offshore wind contracts have already been awarded to companies such as Ørsted (formerly

DONG Energy) and ENGIE.

In parallel, offshore wind costs have halved in recent years to under £58 per MW, making such investments

even more cost-effective.

A key difference between 3G and 4G

is that 4G Heat Networks are inclusive,

whilst 3G networks are exclusive.

Growing complexity of energy networks

As electricity consumption increases to power more and more ‘gadgets’ and electric vehicles, it is doubtful

the existing power grids will be able to meet demand.

Moreover, the growing production of renewable energy sources (many of which are intermittent) drives the

transition of the whole electricity sector to smart electricity grids with decentralised producers that will manage

both demand and surplus energy. This digitalisation, in addition to the necessity of the grid decarbonisation,

drives the different energy sectors (electricity, gas, heat) to team up to coordinate energy production with

consumption; this may benefi t from the new generation of heat networks that include stabilisation factors.

A key difference between 3G and 4G

is that 4G Heat Networks are

whilst 3G networks are


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For example, when the wind isn’t blowing suffi ciently to meet power demand, another energy source needs

to come into play. Fast-acting gas fi red power stations are currently an important ‘stabilising’ factor as they are

able to ‘kick in’ at a moment’s notice - though, most of the time, much of the heat generated by this process

is not utilised like in CHP systems.

A better option is to make wider use of CHP in power

stations and more locally in buildings to provide the

required stabilisation whilst also producing heat that

can be used in the heat network. Using local CHP

very close to the building(s) being served will minimise

distribution losses.

The increased diversity of energy sources also

contributes to complexity, insofar as the traditional

heat sources of CHP and boilers will be joined by

technologies such as heat pumps, solar thermal

and/or PV, electric cells, waste heat etc.

Moreover, as buildings are designed to be more effi cient through better insulation and lean design, they

will have renewable energy sources built in, reducing the demand from the wider network. They may also

contribute any surplus heat or power back to the grid. So buildings will become more sustainable, being both

consumers and producers.

Planning for energy storage

As noted above, one of the main challenges posed by intermittent renewable energy sources - such as wind,

solar and tidal - is that times of highest generation may not coincide with times of maximum demand – for

example at night when winds may be highest but power consumption is low.

It is therefore essential to have a reliable and cost-effective way to store this energy until it is needed. Batteries

are often seen as the obvious way to store electrical power; however, this is far from economical. Studies have

shown that storing the energy as hot water is at least 100 times less costly than battery storage.

Thus, 4G Heat Networks will be able to exploit surplus electrical power by converting it to heat energy for

storage. Ideally, this will be achieved using thermal stores utilising low energy technologies such as heat

pumps, though electric boilers would be another option.

In order to minimise distribution losses, such energy storage should be local to the building – either at the

site of the building itself or close to a nearby energy centre. This has serious implications for building design,

as provision must be made for considerably higher volumes of stored heat energy than would traditionally

be the case.


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In this respect the amount of thermal energy stored is determined by the physical volume of the stored hot

water and the differential (ΔT) between the temperature of the stored hot water (around 80°C) and the return

water temperatures of the system. Low return temperatures (ideally 20°C) will therefore help to maximise

the benefi ts of the energy store.

Electricity from renewable sources can also be converted to gas through

electrolysis (usually methane or hydrogen; sometimes called windgas if the

electrical power is from wind). The gas can then be stored or injected into

the gas grid utilising the current infrastructure.

Renewable electricity gas generation is growing in use and it reinforces the

need to create fl exible 4G Heat Networks that integrate electricity, power

and gas grids. It also reinforces the importance of keeping an open mind

with regards to the energy sources that may be available in the future -

and designing accordingly.

Low temperature operation

With each new generation of heat network, a key driving force has been the desire to improve effi ciency,

recognising that both heat supply and distribution are more effi cient at lower temperatures. Beyond this,

the use of lower temperatures opens the door to low carbon technologies that require lower

temperature operation.

In its Applications Manual AM12 ‘Combined Heat and Power

for Buildings’, the Chartered Institution of Building Services

Engineers (CIBSE) recommends operating temperatures for

radiator circuits to be 70°C fl ow and 40°C return for new

district heating systems/heat networks. The recommended

maximum return temperature from instantaneous domestic

hot water heat exchangers is 25°C.

4G Heat Networks will take the principle of low temperatures much further, using fl ow temperatures of

50°C with return temperatures perhaps as low as 20°C. In doing so, it will facilitate the inclusion of current

and future renewable and low carbon technologies that require lower operating temperatures.

Low return temperatures help to improve the effi ciency of other heat sources. For instance, the optimum fl ow

and return water temperatures for gas-fi red condensing boilers and condensing CHP are 55°C/30°C; for heat

pumps 40°C/35°C.

So, networks built today to operate at lower temperatures with these current technologies will still benefi t

from higher effi ciencies now and can be easily upgraded to use low temperature heat pumps and waste

heat sources in the future.

70 40


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Heatstorage

CHP coalCHP oil

Heatstorage

CHP wasteCHP coal

CHP oil

CoalWaste

Local District Heating District Heating District Heating District Heating

Dist

rict h

eatin

g gr

id

Dist

rict c

oolin

g gr

id

CHPbiomass

2-wayDistrictHeating

Centralisedheat pump

Futureenergysource

CoalWaste

BiomassCHP Biomass

Industry surplus

Gas, WasteOil, Coal

PV, WaveWind surplus

Electricity

Geothermal

Large scale solar

Coldstorage

Large scale solar

Industry surplus

CHP wasteincineration

Alsolow energybuildings

Energy

< 200 oC

> 100 oC

< 100 oC

50-60oC (70oC)

Temperature level

1G / 1880-1930 2G / 1930-1980 3G / 1980-2020 4G / 2020-2050

1G: STEAM 2G: IN SITU 3G: PREFABRICATED 4G: 4th GENERATIONSteam system, steam pipes in concrete ducts

Low energy demandsSmart energy (optimum interaction of energy sources, distribution and consumption) 2-way DH

Pre-insulated pipesIndustrialised compact substations (also with insulation)Metering and monitoring

Pressurised hot-water systemHeavy equipmentLarge ”build on site” stations

Development (District Heating generation) /Period of best available technology

Centraliseddistrict cooling plant

Seasonalheat storage

Steamstorage

Heatstorage

Biomassconversion

The lower temperatures also help to reduce the heat losses from distribution pipework.

Tests in Denmark with residential heat networks have shown that fl ow/return water

temperatures of 55°C/35°C reduce heat losses from distribution pipework by around

75%, compared to traditional higher temperature systems (e.g. 80°C/55°C).

The holy grail for 4G Heat Networks is to reduce these, fl ow and return temperatures

even further, to 50°C fl ow/20°C return.

Building design

It is essential to consider that buildings designed now will be part of the building stock for more than 60 years,

contributing to the UK’s carbon emissions throughout this time. The 2050 targets that have already been put

in place should therefore be infl uencing the design of buildings being constructed today.

At the heart of the 4G heat network philosophy is the need to start with a building design that has the

inherent fl exibility to evolve with time and leverage new opportunities for energy and carbon savings as

they become available.

Consequently, 4G heat network design needs to recognise that once buildings and distribution systems have

been constructed it is diffi cult to change them. The inherent fl exibility of such systems is at the energy centre,

which can be upgraded relatively easily and cheaply at any time.

50 20


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Thus, the starting point is the building(s) served by the network, which need to be as energy effi cient as

possible using high thermal insulation standards, heat recovery systems and intelligent controls, while

design for new build buildings should maximise opportunities for natural daylight. Where appropriate,

buildings should also incorporate local heat and power generation technologies in combination with wind,

solar thermal, photovoltaic, air or ground source heat pumps, electric boilers and thermal store. Such local

generation and utilisation of different energy sources, helps to optimise the fl exibility and the heat network

operation, reducing both costs and carbon emissions.

Crucially, buildings that are constructed today and

connected to energy plant using fossil fuels should

be designed in such a way that they can easily

switch to using energy from renewable and waste

heat sources if the energy centre is upgraded

in the future.

To facilitate this, the heat emitters used in buildings should be designed

to operate at lower temperatures than is traditionally the case, to

exploit the benefi ts of low temperature operation already discussed. If

underfl oor heating is used, this will already be designed for low temperature operation. However, if the heat

emitters are to be radiators, these will need to have a larger surface area to ensure suffi cient heat transfer

from the lower temperature water passing through them.

This use of ‘low temperature’ radiators has other benefi ts for applications such as schools and care homes,

where high temperature radiator surfaces pose a safety risk. Rather than encasing the radiators, as is currently

the case to prevent direct access to the radiator, low temperature radiators will be inherently safer.

In parallel with these aspects of the building’s design, provision needs to be made in the design for signifi cantly

higher volumes of thermal storage, as discussed above.

If the building and the distribution system are designed with 4G Heat

Networks in mind, the heat sources become a side issue.

Typical Heat Network Design

EnergyCentre

Dynamicand Flexible

Fixed Long Term Capital Expenditure

Multiple Heat Sources

Distribution PipeworkThermal Store

HeatMeter

HIURadiators / Underfloor

ConsumerZone

Heat NetworkDistribution System

Consumer Threshold


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Measure to manage

To be truly ‘smart’ 4G Heat Networks need to incorporate intelligent metering that goes beyond billing to

provide real-time data on energy consumption in individual apartments/spaces and across the entire network.

Frequent data enables energy monitoring of performance of buildings, helps to

identify opportunities for improvement and allows visualisation of consumption for

each consumer. Smart metering therefore helps to optimise outputs from the energy

centre and across the distribution network, as well as helping consumers to instigate

behavioural changes to reduce their energy consumption.

Exploiting waste heat opportunitiesCurrent and future heat networks will play a vital role in meeting the UK’s carbon reduction targets, as laid

down in the Climate Change Act 2008. Through the Heat Networks Investment Project, £320m of capital

funding is available to support heat network projects due to be deployed in the next few years.

The problem here is that the HNIP only included large schemes, not small-scale block networks. There were

also diffi culties in accessing the available funds.

Whatever the source of the investment, if such investment is to yield maximum returns and enable a

cost-effective transition from fossil fuels to local renewable and secondary heat sources, such projects

need to incorporate the characteristics of 4G Heat Networks.

Achieving this in practice will require the collaboration of all stakeholders from building owners/operators

and architects through to planners, builders, engineers and maintenance contractors.

It also necessitates a change from the ‘bigger is better’ mindset to take advantage of the potential for many

relatively small block heating schemes. Such schemes are more commercially viable than extensive city-wide

schemes and ideally placed to take advantage of local renewable and heat sources.

A key tenet of the 4G approach is the ability to make use of whatever

energy sources are available locally – the more distant the energy source,

the higher the distribution losses and the lower the overall effi ciency

of the system.


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Inevitably such local energy sources will vary considerably from one area to another, the following

are just some examples:

• Electrical power from wind, solar, tidal sources.

• Waste heat from factories, waste incinerators and large

computer facilities (server farms).

• Heat from biomass sources.

• Heat from solar thermal.

• Heat from geothermal and groundwater sources

• Heat and power from CHP plant.

• Heat from heat pumps driven by renewable electricity.

• Traditional fossil fuel heat sources.

Making 4G Heat Networks a realityAs already discussed, heat networks tend to be either large district heating schemes or small block heating

schemes, and both have potential benefi ts.

The greatest potential for larger district heating schemes is where there is a low-cost heat source relatively

close to the buildings that will be connected to the heat network. Obvious examples include a power station

producing waste heat that can be captured and used in the heat network - or surplus heat from industrial

processes and/or waste incineration.

For such schemes to be viable it is essential they have a source of low cost heat, because of the cost and

disruption of constructing the distribution infrastructure.

Where such low cost heat sources are not available locally it will generally be more practical to consider smaller

schemes – often known as block heating or communal heating. These are very straightforward and require

only the installation of heating and hot water pipes in the building, creation of an energy centre (typically

on the same site) and provision of heat interface units in each space being heated.

Consequently, block heating schemes are commercially viable and easy to implement, compared to large

district heating schemes. As many cities in the UK seek to use brown fi eld sites for small housing developments

(20-25 dwellings) there is considerable scope for the creation of small, smart 4G Heat Networks.

District Heating Block Heating


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Does scale matter in heat networks?

Block heating: West Bridge Mill

West Bridge Mill in Kirkcaldy is an

example of the potential for small

block heating scheme. This is a multi-

residential development which involved

refurbishment of a former B-listed

rope mill. It comprises 16 separate

fl ats housing vulnerable young people.

Electrical power and hot water for

space heating and domestic services

are generated by CHP, with heating

and domestic hot water in each

apartment being managed through

heat interface units (HIUs).

The CHP meets over 70% of the site’s electrical demand and any surplus heat generated is stored at 80-85°C.

This thermal storage reduces the use of back-up gas boilers.

Data from the daily operation of the CHP system can be read on site and is also transmitted via the internet

to a monitoring station. As well as reducing annual CO2 emissions by around 100,000 kg, this block heating

scheme is providing residents with signifi cantly cheaper space heating, hot water and electricity than if they

were using mains gas and electricity.

72%77%

67%

29%41%

53%

65%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

180,000

2011 2012 2013 2014 2015 2016 2017

Building Power Consumption CHP Heat Production [kWh]

CHP Electricity Production [kWh] % Contribution on electricity

West Bridge MillBuilding electricity consumption & CHP contribution


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Multiple block heating evolving to district heating: Aberdeen Heat & Power

As new block heating schemes are

developed in the same locality, they

may be joined to form larger district

heating networks. This is illustrated by

the Aberdeen Heat & Power district

heating scheme.

In the fi rst phase of this project,

electric heating in around 2,350

apartments in 33 multi-storey blocks,

and 15 public buildings, has been

replaced with a heat network based

on block heating schemes and

served by CHP.

Following these initial block heating phases Aberdeen Heat & Power has continued to develop its heat

network to create a wider district heating scheme, adding a further four blocks of fl ats and another

fi ve public buildings.

The result is that typical fuel costs to tenants have been reduced by

as much as 50%!

District heating: Fredericia, Denmark

In time, smaller district heating

schemes can be combined to create

larger schemes that continue to deliver

the key benefi ts of 4G Heat Networks.

The Fredericia district heating

scheme in Denmark, for example, is

a consumer-owned district heating

company suppling heat and hot water

to connected properties. Around 99%

of the heat load for the connected

properties is met by a combination of

waste heat, CHP and the surplus heat

from a local oil-refi nery.

This is one of eight local district heating companies that are connected to the regional heat transmission

system TVIS, which serves 83.000 homes. The fact that all district heating (DH) companies in the area are

interconnected through one system, enables effi cient use of the surplus heat which would otherwise have

gone to waste.


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SummaryDuring their long history, heat networks have evolved to meet a range of demands, which include energy

effi ciency, costs, space, environmental impact and health & safety.

Whilst 3G heat networks are able to address some of these requirements in a limited way, they lack the

key ingredients for a fl exible, responsive and sustainable system that continues to evolve. In short, in terms

of heat network evolution, they are a ‘dead end’.

With an overarching need to reduce carbon emissions, it is essential to plan and manage a transition to

4G Heat Networks within smart energy systems that combine and co-ordinate production and consumption

among heating, electricity, gas and transport systems.

Such sustainable systems will focus on the wider use of low grade renewable and waste heat sources to a

greater extent than ever before, with the ability to manage intermittent energy sources, so every aspect of

the system design needs to address this.

More effi cient buildings with low energy requirements, and onsite energy generation and thermal storage, and

heating systems designed for low temperature operation will be served by highly insulated distribution systems

with low heat losses, from an energy centre that is able to utilise a range of constant and intermittent local

energy sources.

As such, 4G Heat Networks will also underpin the creation of smart, sustainable energy systems based on

low temperature heat networks interacting with low energy buildings to deliver a range of key objectives

that include:

• Cheaper energy

• Lower carbon energy

• Reduced energy imports

This will also lead to variable solutions according to specifi c regional demands, as well as a new approach

to the roles of the energy market, public knowledge and market regulations.

Gas

Electricity

Heat

Network Fusion 4G


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References• 4th Generation District Heating (4GDH) Research Centre, http://www.4dh.eu/

• Paper: 4th Generation District Heating (4GDH): Integrating smart thermal grids into future sustainable energy systems

• The ADE, Market report: Heat Networks in the UK, Published 31 January 2018

• The ADE, Shared Warmth | A heat network market that benefi ts customers, investors, and the environment,

Published 31 January 2018

• BEIS, Heat Networks Consumer Survey: consumer experiences on heat networks and other heating systems,

Published 7 December 2017

• BEIS, Heat Networks Investment Project (HNIP), Published 7 April 2017

• Climate Change Act 2008

• Committee on Climate Change, https://www.theccc.org.uk/

• Department of Development and Planning, Aalborg University, Denmark, http://www.en.plan.aau.dk/

• Department of Civil Engineering, Technical University of Denmark, http://www.byg.dtu.dk/english

• Danfoss District Energy, Denmark, http://districtenergy.danfoss.com/#/map

• Kamstrup District Heating, Denmark, https://www.kamstrup.com/en-uk/business-areas/heat-metering/district-heating

• Jan Eric Thorsen, Oddgeir Gudmundsson and Marek Brand, Danfoss District Heating Application Centre, DK-6430

Nordborg, Denmark, Distribution of district heating:1st-4th generation

• CIBSE AM12 2013

• CIBSE Heat Networks CoP for the UK 2012

• SAV Systems ‘Delta T’ Design Guide 2014

• SAV CPD: SAV-Danfoss FlatStations - 4G Lean Heat Network Design

This document is based on the best knowledge available at the time of publication.

For further information please contact:

Head Office: SAV Systems

Scandia House, Boundary Road

Woking, Surrey GU21 5BX

Tel: +44 (0)1483 771910

Web: www.sav-systems.com E-mail: [email protected] LinkedIn: www.linkedin.com/company/sav-systems

South West: SAV Systems

16 Gay Street,

Bath BA1 2PH

Tel: +44 (0)1225 418079

North West: SAV Systems

11 St John Street,

Manchester M3 4DW

Tel: +44 (0)161 870 6943

Scotland: SAV Systems

49 Manor Place,

Edinburgh EH3 7EG

Tel: +44 (0)131 220 2894

170038 4G Heat Networks - sav-systems.com · Strategic review of 4G Heat Networks in the UK 2...

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