IEEE Power & Energy Magazine - January/February 2017 - 31

In district heating systems, heat is stored in the pipelines
and also in the building envelopes, resulting in a daily profile with
little variation-mainly driven by ambient temperature variations.

Flexibility from heating and cooling can be used in several
ways in a power system. Moving loads from electricity net
load peaks to net valleys can smooth variations. When the
heating devices have suitable controllability, they can also
be valuable sources of reserves that mitigate forecast errors
and faults. Because heat is such a diverse and heterogeneous
load, a selection of system studies and applications is presented in the following to highlight how heat flexibility can
potentially be harnessed.

Integrated Energy System Studies
Electricity System Benefits of
Heat-Pump Deployment in Belgium

Belgium is a densely populated country with significant
plans for variable-power generation. Cost-effective integration will be a challenge; consequently, there is strong interest in finding workable sources of flexibility. In one study,
the deployment of 1-GW electricity from flexible heat pumps
managed to reduce curtailment of variable generation and
avoided 100 GWh of gas-fired generation. However, it was
identified that performing demand response with the heat
pumps increased the building's heat demand by 1-10%. This
increase in electricity use poses a challenge in terms of compensating consumers for participating in demand response,
especially since residential consumers are typically exposed
to prices higher than wholesale market prices. Another case
study shows that the contribution to the peak demand in
winter due to electrical space heating can be significantly
reduced, by 2 GW on a total of 16.5 GW.
Integration of Heat and Electricity Sectors
in the United Kingdom

In the United Kingdom, over 80% of households use natural gas for space and water heating, and this consumes
more than 1.5 times more energy than U.K. electricity consumption. Peak heating requirements in winter are more
than five to six times higher than electricity peaks. While
the electrification of heat could, in principle, provide flexibility to the power sector, the danger is that if electric
heating is uncontrollable, it will magnify power system
variability and peak demand. Additionally, the parallel
deployment of wind and solar power, in combination with
relatively inflexible nuclear generation, could exacerbate
flexibility demand. Studies suggest that, in an inflexible
U.K. electricity system having 30 GW of variable renewjanuary/february 2017

ables in combination with inflexible nuclear generation,
more than 25% of wind energy may need to be curtailed if
no additional measures are taken.
In this context, a well-designed integration of heat and
electricity systems can lead to a more cost-effective transition toward a low-carbon energy system (see Figure 8). When
heat is supplied by heat pumps via district heating systems
or through a controllable electric heating device at customer
premises, analysis demonstrates significant benefits accrued
from three sources:
1) There will be less need for heat production capacity
when heat storages that use electricity cut peaks.
2) Curtailment of renewable generation is reduced when
heat storages can utilize excess generation.
3) With reduced curtailments, less renewable generation
capacity is needed to meet emission reduction targets.
Heat Versus Other Flexibility Sources
in the North European Context

The value of flexibility from the heat sector is influenced
by the cost-effectiveness and availability of flexibility from
other sources. In a Northern European study, a combined
generation-planning/operational model was used to evaluate
the benefits of adding heat pumps, electric heat boilers, and
heat storages to a district heating system in a future where
there would be much greater variable generation in the system. The results demonstrated that, while new transmission
lines probably have the best cost-benefit ratio, heat-sector
flexibility comes as a close second, far ahead of electricity

14
Saving in RES
Integration Cost (£/MWh)

Harnessing Heat Flexibility

12
10

Backup
Balancing (OPEX)
Balancing (CAPEX)

8
6
4
2
0

2030

2050

figure 8. The reduction in integration costs of renewable
generation (electricity sector only) enabled by the integrated operation of heat and electricity sectors.
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017