IEEE Power & Energy Magazine - January/February 2017 - 27

Electric storage heaters make use of the solid materials
around the resistance heater as a heat store and may utilize a fan
to release the heat in a more controlled manner.
systems inherently have considerable flexibility, and planning boils down to managing supply and storage infrastructure, as with most commodities. On the other hand,
electricity-fueled heaters/coolers require the power system
to balance supply and demand instantaneously, changing the
dispatch in the short run and impacting the generation portfolio in the long run.
Electric heating, if deployed in an uncoordinated manner, requires additional power-system flexibility to meet
daily, seasonal, and annual variations. For example, in
France most residential heating is based on electric heating
and causes considerable temperature sensitivity in the power
demand (2,300 MW/°C); this represents a major driver for
extreme peak loads and security of supply.
However, a controllable electric heating/cooling can
draw on the potential flexibility of heating (thermal inertia) to facilitate renewables integration and manage peak
loads. For example, some demand-side management programs are being carried out in France as ad hoc measures
to improve flexibility. In another example from Germany,
it was realized that electric overnight storage heaters can
be a valuable source of flexibility, so an earlier decision to
remove them was reversed in 2013. The use of information
and communications technologies in electric heaters could,
therefore, provide the option to shift demand loads according to power system conditions, while also meeting the
building occupants' comfort requirements. These examples illustrate the strong interaction between residential
electric heating and the power sector, but they also raise the
question on how such integration of electric heating should
be managed to provide flexibility in the most cost-effective
and nonintrusive manner.
Electric heating systems are mostly based on resistance
heaters (including electric storage heaters) and on the more
efficient heat pumps. Heat pumps make use of the natural temperature difference between the outdoors and indoors during a
condensation/evaporation cycle. The heat cycle only requires
electricity to run the compressor and other auxiliary equipment, thereby producing two to four units of heat for each unit
of electricity consumed in air-source heat pumps (although
the gain tapers off in colder temperatures). The efficiency can
be even higher for ground-source heat pumps, reaching performance coefficients of four to five. This minimizes generation requirements and peak load but will not allow as much
flexibility to utilize excess renewable electricity.
Local cooling is usually provided by heat pumps (either
with air conditioning systems that only cool or by reversible
january/february 2017

heat pumps that can also heat). When the heat pump is used
in cooling mode, it is called a chiller. The energy efficiency
ratio is typically lower, ranging 1.5-2.5 units of cooling for
one unit of electricity. In regions with high cooling loads,
the coordinated cooling of buildings results in the dominant
peak electricity demand.
In many cases where a heat pump is installed, it is
complemented by use of an electrical resistance heater or
a gas boiler. The combination with a gas boiler (the socalled "hybrid" heat pump) shows vast flexibility potential. Its smart integration into the electric system could
enable the power system to access the flexibility of the gas
system by switching from the heat pump to the gas boiler
whenever the electricity system is under stress (this could
represent an extended period of several days). Hybrid fuel
boiler/resistance heater systems could provide the option
of using excess renewables by switching from fuels (often
gas) to electricity.
Thermal storage in buildings can enable the optimization
of electricity consumption and charging based on electricity
market prices while still providing thermal comfort to the
user. If the resistance heater is integrated with high-thermalcapacity materials, then the heaters are referred to as storage heaters. Electric storage heaters make use of the solid
materials around the resistance heater as a heat store and
may utilize a fan to release the heat in a more controlled
manner. Using resistance coils or hydronic systems in underfloor heating enables some energy to be stored in the thermal
capacity of the floor as well. Other technologies for thermal
storage include water storage tanks and solid materials. In
particular, in hydronic systems, a water tank can be added
relatively easily, although there is a cost related to the space
use in addition to the cost of the storage device.
Energy can also be stored with a cold storage. Temperature differences are smaller than in heating though; consequently, cold storages would need more volume for the same
energy content. However, it is possible to take advantage
of the latent heat of freezing/melting, which corresponds
to approximately 80 °C of the temperature difference in
water. Available commercial chillers use ice storage; these
can achieve more operating hours, and, consequently, the
chiller can be downsized while also decreasing electricity
use during daily peaks compared to traditional air conditioning. Conceivably, these chillers could also offer flexibility for higher shares of wind and solar power, although
there would probably be a different optimum in the sizing
of the components.
ieee power & energy magazine

27



Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2017

IEEE Power & Energy Magazine - January/February 2017 - Cover1
IEEE Power & Energy Magazine - January/February 2017 - Cover2
IEEE Power & Energy Magazine - January/February 2017 - 1
IEEE Power & Energy Magazine - January/February 2017 - 2
IEEE Power & Energy Magazine - January/February 2017 - 3
IEEE Power & Energy Magazine - January/February 2017 - 4
IEEE Power & Energy Magazine - January/February 2017 - 5
IEEE Power & Energy Magazine - January/February 2017 - 6
IEEE Power & Energy Magazine - January/February 2017 - 7
IEEE Power & Energy Magazine - January/February 2017 - 8
IEEE Power & Energy Magazine - January/February 2017 - 9
IEEE Power & Energy Magazine - January/February 2017 - 10
IEEE Power & Energy Magazine - January/February 2017 - 11
IEEE Power & Energy Magazine - January/February 2017 - 12
IEEE Power & Energy Magazine - January/February 2017 - 13
IEEE Power & Energy Magazine - January/February 2017 - 14
IEEE Power & Energy Magazine - January/February 2017 - 15
IEEE Power & Energy Magazine - January/February 2017 - 16
IEEE Power & Energy Magazine - January/February 2017 - 17
IEEE Power & Energy Magazine - January/February 2017 - 18
IEEE Power & Energy Magazine - January/February 2017 - 19
IEEE Power & Energy Magazine - January/February 2017 - 20
IEEE Power & Energy Magazine - January/February 2017 - 21
IEEE Power & Energy Magazine - January/February 2017 - 22
IEEE Power & Energy Magazine - January/February 2017 - 23
IEEE Power & Energy Magazine - January/February 2017 - 24
IEEE Power & Energy Magazine - January/February 2017 - 25
IEEE Power & Energy Magazine - January/February 2017 - 26
IEEE Power & Energy Magazine - January/February 2017 - 27
IEEE Power & Energy Magazine - January/February 2017 - 28
IEEE Power & Energy Magazine - January/February 2017 - 29
IEEE Power & Energy Magazine - January/February 2017 - 30
IEEE Power & Energy Magazine - January/February 2017 - 31
IEEE Power & Energy Magazine - January/February 2017 - 32
IEEE Power & Energy Magazine - January/February 2017 - 33
IEEE Power & Energy Magazine - January/February 2017 - 34
IEEE Power & Energy Magazine - January/February 2017 - 35
IEEE Power & Energy Magazine - January/February 2017 - 36
IEEE Power & Energy Magazine - January/February 2017 - 37
IEEE Power & Energy Magazine - January/February 2017 - 38
IEEE Power & Energy Magazine - January/February 2017 - 39
IEEE Power & Energy Magazine - January/February 2017 - 40
IEEE Power & Energy Magazine - January/February 2017 - 41
IEEE Power & Energy Magazine - January/February 2017 - 42
IEEE Power & Energy Magazine - January/February 2017 - 43
IEEE Power & Energy Magazine - January/February 2017 - 44
IEEE Power & Energy Magazine - January/February 2017 - 45
IEEE Power & Energy Magazine - January/February 2017 - 46
IEEE Power & Energy Magazine - January/February 2017 - 47
IEEE Power & Energy Magazine - January/February 2017 - 48
IEEE Power & Energy Magazine - January/February 2017 - 49
IEEE Power & Energy Magazine - January/February 2017 - 50
IEEE Power & Energy Magazine - January/February 2017 - 51
IEEE Power & Energy Magazine - January/February 2017 - 52
IEEE Power & Energy Magazine - January/February 2017 - 53
IEEE Power & Energy Magazine - January/February 2017 - 54
IEEE Power & Energy Magazine - January/February 2017 - 55
IEEE Power & Energy Magazine - January/February 2017 - 56
IEEE Power & Energy Magazine - January/February 2017 - 57
IEEE Power & Energy Magazine - January/February 2017 - 58
IEEE Power & Energy Magazine - January/February 2017 - 59
IEEE Power & Energy Magazine - January/February 2017 - 60
IEEE Power & Energy Magazine - January/February 2017 - 61
IEEE Power & Energy Magazine - January/February 2017 - 62
IEEE Power & Energy Magazine - January/February 2017 - 63
IEEE Power & Energy Magazine - January/February 2017 - 64
IEEE Power & Energy Magazine - January/February 2017 - 65
IEEE Power & Energy Magazine - January/February 2017 - 66
IEEE Power & Energy Magazine - January/February 2017 - 67
IEEE Power & Energy Magazine - January/February 2017 - 68
IEEE Power & Energy Magazine - January/February 2017 - 69
IEEE Power & Energy Magazine - January/February 2017 - 70
IEEE Power & Energy Magazine - January/February 2017 - 71
IEEE Power & Energy Magazine - January/February 2017 - 72
IEEE Power & Energy Magazine - January/February 2017 - 73
IEEE Power & Energy Magazine - January/February 2017 - 74
IEEE Power & Energy Magazine - January/February 2017 - 75
IEEE Power & Energy Magazine - January/February 2017 - 76
IEEE Power & Energy Magazine - January/February 2017 - 77
IEEE Power & Energy Magazine - January/February 2017 - 78
IEEE Power & Energy Magazine - January/February 2017 - 79
IEEE Power & Energy Magazine - January/February 2017 - 80
IEEE Power & Energy Magazine - January/February 2017 - 81
IEEE Power & Energy Magazine - January/February 2017 - 82
IEEE Power & Energy Magazine - January/February 2017 - 83
IEEE Power & Energy Magazine - January/February 2017 - 84
IEEE Power & Energy Magazine - January/February 2017 - 85
IEEE Power & Energy Magazine - January/February 2017 - 86
IEEE Power & Energy Magazine - January/February 2017 - 87
IEEE Power & Energy Magazine - January/February 2017 - 88
IEEE Power & Energy Magazine - January/February 2017 - 89
IEEE Power & Energy Magazine - January/February 2017 - 90
IEEE Power & Energy Magazine - January/February 2017 - 91
IEEE Power & Energy Magazine - January/February 2017 - 92
IEEE Power & Energy Magazine - January/February 2017 - Cover3
IEEE Power & Energy Magazine - January/February 2017 - Cover4
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091020
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070820
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050620
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030420
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010220
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091019
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070819
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050619
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030419
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010219
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091018
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070818
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050618
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030418
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010218
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091017
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070817
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050617
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030417
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010217
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091016
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070816
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050616
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030416
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010216
https://www.nxtbook.com/nxtbooks/ieee/powerenergy_010216
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091015
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070815
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050615
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030415
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010215
https://www.nxtbook.com/nxtbooks/pes/powerenergy_111214
https://www.nxtbook.com/nxtbooks/pes/powerenergy_091014
https://www.nxtbook.com/nxtbooks/pes/powerenergy_070814
https://www.nxtbook.com/nxtbooks/pes/powerenergy_050614
https://www.nxtbook.com/nxtbooks/pes/powerenergy_030414
https://www.nxtbook.com/nxtbooks/pes/powerenergy_010214
https://www.nxtbookmedia.com