5 Technology assessment
The Energy Masterplan area has a wealth of resources available which could be developed into low carbon heat and energy projects. This section of the document presents a qualitative technology assessment, which provides an indication of the overall suitability for several technologies in the Energy Masterplan area.
Technologies are presented in the following groups:
- Energy efficiency
- Heat pumps
- Waste heat recovery
- Renewable energy
- Biomass and biofuel
- Electric boilers
- Energy infrastructure
- Traditional fuels
More than 40% of Scotland's GHG emissions are as result of the heating, lighting, and ventilation of buildings. Retrofitting existing buildings to reduce heat demands is an important step alongside transitioning heating systems to low and zero carbon heating technologies. The energy efficiency improvement of buildings in Scotland is supported by the Energy Efficient Scotland Programme. Pre-1919 tenements and other stone constructed houses and commercial buildings which are commonly found within the Energy Masterplan area are the most difficult to treat in terms of developing and implementing appropriate and cost-effective energy efficiency solutions. These properties are often not suited to cavity wall insulation or external wall insulation. There are also other significant issues such as ownership titles, common ownership, turnover and obtaining financial contributions from multiple different owners. The replacement of single glazed windows can also be problematic and expensive in conservation areas.
Heat pumps are a proven low carbon heat technology for the Energy Masterplan area. By extracting the low-grade heat from different sources through an electrically-driven compression cycle, heat pumps can deliver very efficient electrical heating – typically more than three times more efficient than conventional electric resistive heaters.
Water Source Heat Pumps
Surface-water heat pumps can play an important role in decarbonising the Energy Masterplan's heat sector particularly when connected to a district energy network in a densely populated urban environment. Water-source heat pumps can be a more efficient alternative to air source heat pumps as the River Clyde remains warmer than air on the coldest days.
There are several technical, economic, and environmental considerations which need to be accounted for when assessing the feasibility of a river-source heat pump, these include:
- Tidal or not: The River Clyde is tidal up to the Weir at Glasgow Green in the heart of the city. The minimum water level will need to be established to determine the feasibility of abstraction from the river. If the river is tidal at the point of abstraction under consideration, the Crown Estate Scotland may own the seabed and/or the foreshore, therefore an occupancy agreement may be required from the Crown Estate Scotland. Permission from the harbour/port authority may also be required. A marine licence is required for construction, alteration or improvement works required below the mean water high springs (MHWS) tide.
- SEPA: For inland open loop surface water heat pumps, the abstraction volume will determine the level of authorisation required under Water Environment (Controlled Activities) (Scotland) Regulations 2011 (CAR). A point source simple licence would be required if the temperature change exceeds 3°C. For coastal and transitional abstractions, an abstraction registration is required and a point source simple licence if the ∆T between the abstraction and discharge exceeds 3°C.
- Water salinity and quality: The water quality in the area will determine the filtration requirements. The abstraction of seawater, for example, locations on the River Clyde downstream of the weir at Glasgow Green where seawater is present, will require the use of more expensive corrosion resistant equipment on the abstraction-side of the heat pump.
- Filtration requirements: A very fine filter is likely to be required to prevent fish abstraction, mussel seed entering and fouling the heat exchanger as well as silt.
- Preferred abstraction and discharge structure: a bank-side intake structure will be less complex and costly compared to a submerged "in-river" intake.
- River temperature profile and variability with depth: The source-temperature will influence the efficiency of the water-source heat pump therefore the temperature profile may dictate the location of the abstraction point from the river. The source temperature will also influence the running hours and heat output. According to CIBSE CP2 for the purpose of feasibility studies assuming a ∆T of ±3°C is a reasonable starting point. This will need to be discussed in more detail with SEPA as projects progress.
- Heat network flow and return temperatures: the river-source heat pump will operate more efficiently, the smaller the temperature difference between the source and load-temperature.
Other factors which should be considered include the ground conditions where the energy centre will be located. Ground conditions near the riverbank tend to be poor and often require extensive piling to enable construction. These challenges are not unique to water-source heat pumps but rather riverside developments in general.
Waste Heat Recovery
There are assets along the River Clyde that produce waste heat. These assets could potentially provide low carbon heat to buildings, particularly where they are located in close proximity to clusters of high heat demand density where a heat network may be viable.
- Wastewater Treatment Works (WWTW)
- Industrial process heat recovery
- Energy from Waste (EfW)
Heat can be recovered from wastewater and upgraded using water-source heat pumps. Scottish Water Horizons are actively identifying opportunities to serve heat demand clusters in close proximity to their wastewater treatment works using water-source heat pumps. The benefits of using wastewater from WWTWs include the stable year-round temperature which can deliver high seasonal COP as a result.
The recovery of waste heat from industrial processes can provide a cost-effective heat source to heat networks and also an additional revenue stream for the industry providing the waste-heat. An important consideration when exploring waste-heat recovery opportunities from industrial processes is the quality and quantity of heat available to the heat network and also the proximity of the waste-heat source to the heat demand cluster.
The Draft Heat in Buildings Strategy specifically references the important role which heat recovered from EfW will play in Scotland's heat networks. The Scottish Government has set out in Scotland's Fourth National Planning Framework: Position Statement that a potential change to planning policy will be to encourage applications for EfW facilities to provide a connection to a heat network. The Scottish Government will consult in 2021-2022 on whether there is need for further regulatory measures or support measures to increase the capture of waste or surplus heat, for example from Energy from Waste plants, to be supplied and/or used through heat networks. There are two EfW plants in close proximity to the Energy Masterplan area. The South Clyde Energy Centre which is not yet operational lies in close proximity to the Queen Elizabeth University hospital as well as the proposed Glasgow Riverside Innovation District. It will have the capability to export up to 35 MWe and up to 12MWth. The Glasgow Recycling and Renewable Energy Centre at Polmadie operated by Viridor handles 350,000 tonnes of waste each year and can generate up to 11 MW of electricity.
There are natural resources available in the Energy Masterplan area which could be used to generate renewable heat and/or electricity.
- Ground mounted solar photovoltaics could potentially be situated in areas of vacant or derelict land to generate renewable electricity.
- Roof-mounted solar photovoltaics could be installed at the building level, where there are accessible, unshaded, south-facing roof area. Local Authorities, Social Housing organisations could consider a programme of roof-top solar PV for their building estates.
- Solar PV carports could be considered in areas where there are carparks, especially where there are Electric Vehicle (EV) charging points.
- Solar thermal collectors may be appropriate for buildings with significant domestic hot water demands, such as pools, gyms, and hotels.
- Wind turbines could potentially be located in rural locations where there are suitable windspeeds and few planning constraints (Section 4.1.5 wind turbine opportunities.)
- Hydroelectric (run of river) projects could be considered where there are suitable flow rates on the River Clyde.
- Electric boilers may form part of a low carbon heating solution. As the electricity grid decarbonises with increasing renewable and low carbon technologies electricity supply to the grid, carbon emissions associated with electric heating are reducing.
- Electric boilers at the building level can remove the need for a natural gas connection however the operating costs of such a system in a residential setting is likely to be high. As part of a low carbon heating approach, electric boilers are likely to provide top-up or backup heating for heat networks where the primary heat supply may be a heat pump or other technology. Power-to-heat technologies such as electric boilers and heat pumps have the potential to enable the integration of large shares of variable renewable energy e.g. wind and solar. Electric boilers offer demand side flexibility particularly when integrated into district heat networks, they can be utilised when there is excess electricity generation and the price of electricity is low and turned off when electricity demand is high, and the cost of electricity is high. Electric boilers are inexpensive but can only generate heat on a ratio of 1:1. In Denmark, there is over 400 MW of electric boilers used in the district heating sector.
Biomass and Biofuel
Biomass and biofuel can form part of a sustainable energy strategy for the Energy Masterplan area – where it is sourced sustainably. Biomass is often purchased as wood chips or wood pellets, while biogas is a gas fuel derived from organic matter such as food scraps or animal waste. These fuel sources can be used in Combined Heat and Power (CHP) units or boilers.
The advantage of a CHP, also known as co-generation, is increased fuel efficiency - heat and power are generated from the fuel, and there are no (or low) transportation losses to the location where it is used, in contrast to a traditional distribution grid with losses over distance. CHPs require a steady base heat load to operate, so tend to be used in energy centres serving distilleries, hospitals, hotels, swimming pools, and other buildings with a steady, diverse heat load.
Tri-generation, delivering electricity, heating, and cooling, is also an option. This can be done by adding cooling to the system, for example, by adding absorption chillers.
- Biomass could potentially be used in the Energy Masterplan area – outside areas where there are air quality concerns such as air quality management areas, and in locations where there is space and access for a woodchip or wood pellet store.
- Biomass CHP capacity is generally in the order of megawatts (MW). These are suited to energy centres with significant heat demands
- Biomass boilers are available in a range of capacities, and they require regular maintenance by a trained service provider to operate well
- Biogas CHPs often use methane gas produced from an anaerobic digestion process
- Biogas boilers are also often paired with an anaerobic digestor. In cases where biogas is flared from sources such as landfills, there could be an opportunity to use a biogas boiler to provide heat instead – where the biogas is of an appropriate quality and flow
Hydrogen is noted in the draft Heat in Buildings Strategy as a longer-term option, best deployed where there is a local supply and/or a concentration of industrial demand. It is likely to play only a limited role before 2030. Therefore, this strategy does not focus on hydrogen as a low carbon heat source for deployment in projects in development. Hydrogen offers opportunities as a fuel and energy store. At the point of use, the combustion of hydrogen produces no carbon dioxide. Over time, hydrogen is anticipated to play an increasing role in the transition to a low carbon economy. In theory, 39 kWh of electricity and 8.9 litres of demineralised water are required to produce 1 kg of hydrogen at 25°C and 1 atmosphere pressure. Typical commercial electrolyser system efficiencies are 56%–73% and this corresponds to 70.1–53.4 kWh/kg. Using water from the River Clyde is likely to require significant treatment prior to its use in hydrogen production. This treatment is likely to increase the cost of the installation and also adversely affect the system efficiency.
- Hydrogen can be produced from industrial processes. One of the proposed projects in the Energy Masterplan area is to produce hydrogen from an existing process. This hydrogen could then be used as a fuel
- Hydrogen fuel cells use an electromagnetic cell to convert the chemical energy of hydrogen into electricity using an oxidation reaction. Fuel cells are useful to generate electricity where hydrogen is available as a fuel
- Hydrogen fuel cell CHPs provide combined heat and power, and are available at the utility, industrial, and commercial scale
- Hydrogen-ready boilers can use either natural gas or hydrogen. These could be used as part of a transition from a natural gas network to a future hydrogen network.
- Electric Vehicle (EV) charging infrastructure, including EV charging points and electricity cabling is useful to consider as part of a programme to transition to EV transportation
- Heat network infrastructure, such as energy centres, networks for heating and cooling, and building connections is integral to low carbon energy plans serving clusters of buildings with dense energy demands
- Private wire, for example, an electricity connection from wind turbines, ground mounted solar arrays, or CHPs to the point of use can be economically beneficial where a direct connection over a relatively short distance is needed
- Thermal Energy Stores (TES) are normally included in heat network projects. They allow heat to be stored when more heat is generated than used, and this heat is used later. TES help to balance demand by allowing a lag between the time of heat generation and heat use.
- Batteries can be useful for small energy consumers where the aim is to maximise onsite use of onsite energy generation from sources such as photovoltaics. In cases where there is some electricity export, batteries could be used to charge during the day and discharge in the evening.
- Hydrogen can act as an energy storage fuel. In the future, hydrogen may play a stronger role in the route to decarbonisation
- Large-scale. In terms of electricity infrastructure, there is a space for energy storage. When grid infrastructure is considered, in the Energy Masterplan area, the following types of storage could be considered in creating a more robust and adaptable energy grid:
- Batteries. This could include Lithium ion batteries, lead batteries, redox flow batteries, vanadium redox flow batteries, nickel-cadmium batteries, sodium sulphur batteries, and others
- Mechanical – Flywheels can be used when short-term backup power is required because utility power fluctuates or is lost
- Mechanical - Compressed Air Energy Storage (CAES) can store energy at a utility scale, using energy generated at periods of low energy demand at times of higher demand
Traditional fuels including natural gas (and natural gas CHP), coal, oil, and nuclear are available; however, they are not recommended as low carbon fuels or low carbon technologies to situate in the Energy Masterplan area. Natural gas, coal, and oil have relatively high greenhouse gas emissions compared to low or zero carbon technologies. A nuclear project would have its own issues around safety, scale, safe storage of waste as well as associated environmental considerations related to waste.
5.2 Qualitative technology multi-criteria analysis
This section assesses potential energy technologies that could be used to supply energy in the area, using a Multi Criteria Analysis (MCA). A range of available heat sources and technologies have been reviewed.
The categories against which the technologies have been assessed are:
- Capital costs: Cost of buying and installing the equipment, with high capital expenditure shown as red and low capital expenditure shown as green
- Operational costs: Typical cost of operating and maintaining the technology, including fuel costs
- Decarbonisation: Impact on carbon emissions. Zero carbon technologies are scored green, whilst technologies that result in carbon emissions above the baseline are scored red.
- Technology risk: Indicating technology maturity in the Scottish market.
- Local environmental impact: Including impacts on local air quality and ecology
- Overall suitability: Technologies suitable in the Energy Masterplan area
Table 5.1 provides a qualitative review for each technology in the context of the Energy Masterplan. A 1-3 scale is used to indicate positive, neutral, and possible negative aspects of the technology that must be considered in the context of the area. The scale is as follows:
- 3 indicates a positive impact, opportunity of advantage of using the technology
- 2 indicates a medium or neutral impact
- 1 indicates potential large challenges and considerations of using the technology
|Capital costs||Operational costs||Decarbonisation||Technology risk||Local environmental||Overall suitability|
|Retrofit buildings to reduce heat demand||2||3||3||3||3||3|
|Air source (ASHP)||3||2||3||3||3||3|
|Ground source (GSHP) - Closed loop||2||2||3||3||3||3|
|Ground source (GSHP) - Open loop||2||2||3||3||3||3|
|Water source (WSHP) - Closed loop||2||2||3||3||2||3|
|Water source (WSHP) - Open loop||2||2||3||3||2||3|
|Waste heat recovery|
|Industrial process heat recovery||3||3||3||3||3||3|
|Wastewater Treatment Works (WWTW)||2||2||3||3||3||2|
|Energy from Waste (EfW)||1||2||3||2||2||2|
|Solar thermal water heaters||3||3||3||3||3||3|
|Hydroelectric (run of river)||2||2||3||3||2||2|
|Biomass and biofuel|
|Biomass Combined Heat and Power (CHP)||2||2||3||1||2||2|
|Biogas Combined Heat and Power (CHP)||2||2||3||2||2||2|
|Hydrogen produced from industrial process||1||2||3||2||3||3|
|Combustion Combined Heat and Power (CHP)||1||1||2||2||3||2|
|EV charging infrastructure||2||3||3||3||3||3|
|Heating or cooling network infrastructure||2||3||3||3||3||3|
|Storage - building scale|
|Thermal Energy Store (TES)||3||3||2||3||3||3|
|Storage - utility scale|
|Mechanical - Flywheel||1||2||2||2||3||2|
|Mechanical - Compressed air||1||2||2||2||3||2|
|Natural Gas CHP||2||3||1||3||2||2|
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