Thermal storage offers significant benefits
to micro CHP for a number of reasons.
Firstly, a substantial thermal store allows
the unit to produce electricity when it is most valuable, and avoid
export to the grid, which in some markets (such as Japan) remains a
A substantial thermal buffer store minimises
cycling, leading to improved engine life, minimising parasitic losses,
and maximising the electrical output of the micro CHP unit. It
also extends the range of potential applications for a given micro CHP
unit as smaller homes can be served without concern for cycling and
larger homes benefit from the stored heat capacity to meet higher peak
loads, (including rapid recovery of domestic hot water), minimising the
use of the supplementary burner usually included in micro CHP systems,
and thus maximising electrical output for a given thermal load.
On a rather prosaic level, thermal storage
also allows the micro CHP unit to be physically separated from the
existing primary heating circuit in the home; this has often proved a
source of contamination leading to reliability and performance issues.
Electrical storage, in combination with
microgeneration, can, in principle, meet the
entire electrical needs of the home without the need for grid
connection, providing "grid independence".
However, the majority of micro CHP
products are currently intended for grid-parallel operation as this
represents by far the biggest market in the developed world.
Despite this, recently there has been a
growing interest, triggered by developments in the German FIT
arrangements for PV systems, towards incorporating some electrical
storage to maximise utilisation of generated power within the home.
This export avoidance mechanism also minimises adverse impacts of PV
generation on the network in summer during low demand periods.
However, this is relatively unimportant for micro CHP which generates
most during peak winter demand periods and when any export is of
significant value to the system.
Beyond this, however, electrical storage can
have significant value in its own right, providing useful services to
the grid and the overall energy system. For more information on
control of micro CHP operation has profound implications both for the
home and for the national electricity network to which it is
From the householders' perspective, the ability to
match generation to demand will enhance the value of the micro CHP
output. From a generator's or network operators perspective, there
are potential benefits in micro CHP acting as a
"Virtual Power Plant", centrally controlled and acting within
the national generation portfolio.
However, whoever has control of
micro CHP generation, there are clearly benefits in aligning output with
periods of high value (economically and environmentally)
Unfortunately, at present the focus seems to
be on optimising load and generation to match generation with household
consumption which, whilst superficially beneficial (at least from the
householders'' point of view) does little to address the significantly
higher value elsewhere within the system.
electricity has been centrally generated and distributed down through
the network to individual consumers, being metered at point of
Entire infrastructures have been developed to measure
and manage this process. The need to measure and attribute an
appropriate value to generation flowing from the home raises challenges
for metering technology and for the related infrastructure.
This is compounded in markets such as the UK
where the energy industry has been fragmented to the extent that it is
extremely time consuming and cumbersome to implement changes to the
metering and settlement system, requiring consensus of numerous parties
with often conflicting interests.
For more on the value opportunities and the
need for reform, see the section on