ENERGY MANAGEMENT
180 160 140 120 100 80
Electric hot water boiler
Air source heat pump
Electric panels/
Electric hot water boiler
Figure 5. Difference of heating fuel costs in France .
heating panels to provide space heating offsetting building fabric and infiltration losses.
l Electric hot water boilers to provide Low Temperature Hot Water (LTHW) heating to air handling unit heating coils.
The electric panel heaters are typically ceiling mounted with heating elements/ mats attached to a metal surface. Additional heating to the spaces is provided through the ventilation system. DHW generation in this approach is via indirect hot water storage electric calorifiers fed by the LTHW system.
Option 4: gas-fired boiler This is the most common heating system in the UK. Thermal energy is generated by a gas-fired boiler utilising natural gas as the fuel for an LTHW distribution and heat emitter system. There are several gas-fired boiler types available, with the main ones including cast iron sectional, cast aluminium, steel sectional and steel shell. DHW generation for the basis of this
review is based on utilising indirect hot water storage electric calorifiers fed by the LTHW system. The system will include boilers, burners, flue systems and incoming gas supply. High efficiency low NOx boilers ensure efficient pre-heating and mixing of air and fuel to reduce greenhouse gas emissions during combustion.
Assessment method A series of technical and financial assessments were undertaken on each of the proposed solutions to allow numerical comparison with respect to financial and carbon implications. Factors that were assessed and contributed to the overall comparisons include the below. l Capital cost of the installation, including: •Heat generating plant and domestic hot water system. •Heating and domestic hot water distribution costs and heat emitters. •Where relevant, electrical
IFHE DIGEST 2021
infrastructure required to support heating system including transformers, generators and enhanced HV distribution as required.
l Maintenance costs are based on a comprehensive component-based review of each proposed system’s constituent parts from main plant and the distribution network. Estimated maintenance costs and frequency of required works were incorporated into the assessment.
l The calculations consider cooling, lighting, auxiliary and equipment energy loads as part of the annual energy consumption.
Capital and maintenance cost of systems The difference in capital and maintenance costs are shown in Figure 1 and Figure 2. These are independent of fuel carbon content and fuel kWh price. The findings indicate that the gas-fired boiler solution has the lowest capital cost and the electric hot water boiler system has the lowest maintenance costs. Capital costs for the all-electric solution is impacted by electrical distribution including additional transformers, generators and infrastructure. In addition, an ASHP solution is significantly more expensive in terms of plant costs. Due to quantity of ASHP units, the maintenance requirements are more extensive. Electric hot water boilers have a lower maintenance cost, due to gas-fired boilers requiring dual fuel burners versus more straightforward boiler maintenance of electric boiler.
Operational costs in the UK At current electricity and gas fuel prices and carbon factors, the running costs in terms of financial, and carbon, are shown in Figures 3 and Figure 4. Annual fuel costs are impacted by the
difference in unit cost of 2.3p/kWh for gas and 17p/kWh for electricity at current UK prices. Carbon emissions are impacted by the difference in unit kgCO2 electricity and 0.18 for gas.
of 0.28 for
Gas-fired boiler
380 330 280 200 180 130 80
Electric hot water boiler
Air source heat pump
Electric panels/
Electric hot water boiler
Figure 6. Difference of annual carbon emissions in France.
The situation in France Of all the countries for which kWh cost and carbon factor data was identified, the low carbon content and relative price for France was chosen for analysis. The findings are shown in Figure 5 and Figure 6.
Annual fuel costs are impacted by the
difference in unit cost of 3.3p/kWh for gas and 14p/kWh for electricity at current prices in France. Carbon emissions are impacted by the difference in unit kgCO2 of 0.047 for electricity and 0.18 for gas.
Impact on distribution networks The switch to providing heat from an electric source has an impact on grid connections. Generally, the electrical maximum demand of the hospital will significantly increase due to the large heating loads that would be fed from the electrical supply. It is important to realise that generally the maximum demand is the absolute worst case anticipated connected load on the hospital. This value should include realistic levels of diversity to account for the operational differences, e.g. from 24-hour accident and emergency departments to day clinics. To mitigate the increase in grid
connection size, ways of reducing the burden on the grid need to be explored. New and innovative low and zero carbon technologies – such as large PV arrays, battery storage, low carbon generators, e.g. hydrogen to electricity and other methods of electrical generation and storage – could be considered to ‘peak lop’ the maximum demand in place of traditional fuel oil generators, which have an adverse effect on any zero carbon target. The general drive for reducing
operational carbon footprint of a building means that increasing numbers of installations are exploring heat generation via electrical sources. The current regional electrical infrastructure in many regions will therefore come under increasing strain. It is imperative that from a building design perspective this is considered.
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Gas-fired boiler
Percentage
Percentage
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