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Electrical Storage | Thermal Storage | Load Management | Metering
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Management
of electrical loads has been practiced in domestic applications for
decades. The most familiar application is the use of electric
storage heaters to shift heating load from daytime periods when
electricity is expensive, to night time (or other off-peak period) when
electricity is relatively cheap. The same concept can be applied
to other loads, and washing machines, for example, often have time
switches on the control panel, in order to delay operation of the
appliance until a suitable off peak period. However, the ability
to match loads to the period of micro CHP generation is
significantly more complex as it operates dynamically to meet heating
requirements. In the case of storage heaters, electricity price
depends on time of consumption, whereas with micro CHP, value depends on
whether generated electricity can be used within the home (where it
avoids purchase at a high price) or whether it is exported to the
network (where it attracts a relatively low price). Less than half
the cost of electricity supplied to the home is for the energy content,
the remainder being transport and other system costs. Suppliers
cannot, therefore, logically offer to purchase power at the same price
they sell it. Early studies showed that the value of micro CHP
generation could be enhanced by load matching, although in practice
utilisation can still only be increased by about 10% to 80%, however
good the control system for a typical home. Indeed the level of
utilisation was, not surprisingly, found to be more influenced by the
amount of power used in the home. It is questionable whether the
cost and complexity, and even lifestyle impacts of such controls is
worth the enhanced generation value.
From a suppliers point of view, however,
the ability to understand, influence and possibly control demand and generation
within the home is of significant value. Furthermore, both generators
and network operators can benefit from the ability to manage loads and
generation embedded within the distribution networks to optimise
utilisation, and hence cost recovery, of their asset investments. |
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LOAD MANAGEMENT |
GENERATION MANAGEMENT |
| Electricity
was initially supplied on an unrestricted basis, with no account taken
of the time of day. In the 1960's, however, the high daytime
demands which resulted in redundant capacity during the night was
addressed by encouraging consumers to adjust their demand to take
advantage of reduced nighttime tariffs. These tariffs were
provided in conjunction with space and water heating devices which
converted electricity into heat at night, which was then released during
the day time and when hot water was required. Initially this was
achieved using simple clocks, but later evolved using radio tele-switching
both to allow remote adjustment of start/stop periods and to stagger the
changeover to avoid short term spikes. These tariffs remain in
place in many EU countries; in the UK the most familiar is "Economy
7" which provides 7 hours of cheap electricity normally between
23.00 and 07.00. In response to a growing awareness of the
further potential for load shifting in the early 1990's, a consortium of
UK electricity companies developed and trialled a sophisticated system (CELECT
acronym for "Control Electric") which integrated day ahead CRM
(Cost Reflective Messages), day ahead temperature forecasts, customer
programmed heating demand and a self learning algorithm which predicted
the thermal response of the home to heat input. The customer
programmed the desired temperatures for each zone (or room) throughout
the day and the programmer then integrated the relevant inputs to
provide the desired temperatures at the lowest possible cost, using a
combination of storage and direct electric heaters.
In 1996, an EU funded project (ETHOS)
took the concept a stage further by including other domestic appliances
into the load management system and a number of manufacturers are
believed to have included the necessary functionality within their
appliances should a common standard be agreed at some future date.
The UK based TAHI project incorporates
load management and the potential for generation management, but as yet
there is no common standard and the need for each appliance to contain
compatible intelligence is something of a barrier to
implementation. The EU funded TAHEA consortium continues to
develop the concept on a European scale. |
Rather
than attempting to modify the behaviour of each individual appliance
within the home (or even of the consumers themselves), a number of
commentators advocate the modification of domestic generation patterns,
either to better match the consumers' pattern, or to modify the
diversified demand profile of a number of conterminous consumers. Clearly this can only be achieved if some
form of energy storage is applied, most likely as thermal inertia of the
system or with a dedicated thermal store.
The section on thermal storage deals with
products for individual homes, but an EU funded project using the
Vaillant fuel cell in conjunction with a substantial thermal store and
supplementary boiler serving a small apartment block, is being operated
as a VPP (Virtual Power Plant). |
| Page update
22nd
August 2008. |
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