Traditional domestic meters simply record
cumulative kWh totals and have no facility to record consumption within a
specific period. Even two-rate meters, such as those used with Economy 7
tariffs, simply record cumulative totals during the on-peak and off-peak
In 2003, the UK implemented a standard
known as P81, which permits the use of Non Half Hourly (NHH) metering for export as well as
import, avoiding the high cost of recording, analysing and
"settling" kWh for each of the 17520 HH periods each year.
In order to correlate the consumption of
domestic consumers using NHH meters, it is necessary to apply
"settlement profiles". These make statistical
assumptions based on historical load research and, in most instances bear
no relation to the actual consumption of any given household.
Currently, the assumed profile for export
comprises two "chunks", one two hour period in the early morning
and another for five hours in the evening, based on the assumption that
all micro CHP generation will occur within the standard seven hour daily
heating period, itself an assumption of a typical household's heating
pattern. Although it is recognised
that this is a crude assumption, it is considered accurate enough for the
very small number of systems currently in operation.
Extensive trials undertaken by BEAMA for the
UK government concluded that such deemed profiles were inappropriate for
microgeneration given the widely varying nature of the technologies.
As outlined above, Half Hourly (HH) meters are used in commercial
installations where the significant amounts of kWh exported in each half
hour period, justifies the cost of such metering and the underlying
In many cases these are provided with Advanced Meter Reading
(AMR)functionality to facilitate readings and minimise errors.
These are available from numerous
manufacturers but are not included here as the related infrastructure is
not currently considered suitable for micro CHP.
HH metering is, however, essential to capture the true
value of a specific microgeneration installation; it allows
consumption to be accurately attributed to the relevant cost period and
hence optimises the value of each customer. It also incentivises
operation of the microgeneration system to deliver optimum value to
either the end user or the energy system as a whole.
many years, the cost and effectiveness of manually reading meters has
been under scrutiny. There are clear advantages to being able to
remotely access meters, including accurate start/end reads with change
of tenancy and change of supply and to avoid the need to estimate
readings when access to the property cannot be obtained.
However, within the current UK market,
the structure of the industry acts as a disincentive to the
implementation of advanced metering. The meters are owned by the
metering company which charges a daily rental to the energy
supplier. If a customer changes supplier (which can in theory take
place every 28 days!), the new supplier may not wish to pay the higher rental
for an advanced meter, particularly if they do not support the related
infrastructure. The meter company then has a stranded asset with
no means of recovering the investment.
Regardless of this, meters are being
developed which can provide a higher level of service. Indeed,
some meters are being developed which provide the functionality not only
to remotely read meters, but also to communicate additional information.
However, the current UK roll out of "smart
meters" is anything but; it simply provides the minimum functionality of
remotely accessible aggregate kWh readings.
to the control and metering of domestic consumers with micro CHP (or any
other form of generation) is the ability to receive and in some cases
A number of options for communication
within the home are being considered including:
1) Power Line Carrier (PLC) which attaches
a carrier signal to the mains cabling and hence has
connectivity to all electrical appliances without the need for
additional wiring. This is probably the simplest and cheapest
system, perfectly adequate for the bandwidth required for load
From the home to the central control, the
1) PLC up to a sub-station from whence
the data is transferred to radio. This has the disadvantage of
requiring high penetration levels to achieve economies of scale and
although successful in countries with monopolistic (Italy, France)
or mandated (Sweden) common infrastructure, is unsuitable for the
2) GSM and GPRS allow the implementation
of incremental capacity, but currently suffer from very high
operational costs, although there is no reason that the structure of
charges could not be changed to reflect the low bandwidth and use of
off-peak communication network capacity.
3) Fixed (telephone) using PSTN or