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Harnessing your spare power

11 November 2010

Thanet Earth

All un-harnessed energy in the UK’s commercial energy assets such as CHP and standby generators could power London. In this month's PFM, Frank Booty asks how power is now being aggregated for the ‘smart grid’ and what are the benefits

IS IT A FANCILFUL IDEA to aggregate energy from existing commercial energy assets such as standby generators, electricity consuming equipment, combined heat and power (CHP) generators and hydro generators, and provide this energy to National Grid to meet its reserve power needs. According to Flexitricity of Edinburgh it is not and it claims to be among the first to bring smart-grid technology to market.What’s more, it estimates that so far its technology has taken 9,000 tonnes of carbon dioxide out of the electricity system.
Flexitricity partners with businesses throughout the UK to provide a low carbon source of reserve ‘flexible electricity’ to the National Grid. The company looks for flexibility in electricity consumption and generation, and creates revenue for energy users and generators using the flexibility it finds.
How does it work? The aggregator communicates directly with standby generators and/or electricity-consuming equipment on partners’ sites via secure internet connections, aggregating them into a ‘virtual power station’.
This enables National Grid to start standby generators and turn down electricity consumption at short notice and for short periods, right across the UK. This is used to keep the national electricity supply stable in times of system stress.
It is a novel concept that requires some questions answered by Flexitricity’s founder and MD, Dr Alastair Martin, and EDF’s services manager Ian Jerwood. (EDF Suez Energy UK, operates a wide range of load management products including STOR(short term operating reserve) frequency control and commercial load management).
Booty: How much does the FM with spare generating capacity/standby generators get from the deal?
Martin: “This depends on the type of capacity, how it operates, the ambition of the site owner, and to a lesser extent, its location. Each megawatt of capacity should net somewhere between £30,000 and £50,000 per annum for the owner of the site, after fuel costs.”
Booty: How do you know when any spare electricity is available?
Martin: “We know through continuous live remote monitoring, which we interpret using information provided by the site owner. We use the live signals together with our models and knowledge of how each site operates to manage the capacity we offer as a reserve service to the national electricity system. We also use it to alert site owners of concerns.”
Jerwood: “Experience of site operation is key for us, however, participants also play an important role through two-way communication with us, especially when ‘out of profile’ operation is expected – typically a maintenance requirement.”
Booty: What does the operator have to do when they have generated too much electricity and the Grid doesn't need any extra? Where does the electricity go?
Martin: “When we run a generator at 8MW, while the site is consuming 7MW, the remaining 1MW will leave the site through the site’s distribution network connection. This electricity will be consumed by the other sites connected to that bit of distribution network. If the site happens to be consuming 9MW at the time that we run the generators, the missing 1MW will enter the site through the site’s distribution network
connection, as it normally would - before we started the generator 9MW was coming in through that connection.
“What National Grid wants is something that reduces the stress in the transmission network. If we run a generator at some site at 8MW, the effect on the transmission networks is a net 8MW improvement, regardless of whether the 8MW was all consumed on the site, all sent out of the site through the site’s meter, or a mixture of the two. We get exactly the same effect by turning down consumption at a site by 8MW. The 8MW
contribution from the site means that the transmission system doesn’t have to supply the 8MW from other power stations. Since National Grid only calls on the site when other power stations are struggling to cope, everyone gets what they need. The detail is a little more complex – the 8MW generated locally doesn’t lose as much energy as it travels, because it doesn’t travel as far. So the effect on National Grid is actually a little bit more than 8MW.”
Jerwood: “At its peak National Grid operates at around 58GW so the odd MW here and there from an individual site does not have any real effect by itself and will form part of the flow of energy. At site level, providing the correct number of MWs when required is more important as the amount of income received is capped. In the case of the example here, at 7MW, it will be burning fuel for free which is not good for the environment nor the company’s bottom line.”
Booty: Running diesel-powered standby generators isn’t very ‘green’
Martin: “Sustainability in energy has three strands. First: consume less. That’s what good energy management is all about. Second: find green sources. That’s why people build wind farms, and are developing wave and tidal energy.The third strand is efficient balancing supply anddemand, and is the least well understood.”
Electricity can’t be stored so consumption and generation have to match in real time. Because of this, the question is often asked, ‘what happens when the wind doesn’t blow?’ In fact this was an issue well before the first wind farm was built. All power stations can and do fail (and the bigger the station, the harder the hit when it fails), and
forecasts of electricity demand will often miss the mark. So the National Grid has to keep something in reserve at all times.
Diesels produce more carbon dioxide when running than modern gas-fired power stations, and less than the current generation of coal-fired power stations. But their key environmental contribution comes when they are not running, that is around 99 percent of the time. Merely by being available - ready to start, but burning no fuel - they remove the need for National Grid to hold reserve elsewhere. The ‘elsewhere’ is running fossil-fuelled power stations at part load (to create headroom), which is much less efficient
than when running at full load. If not enough power stations can be operated in that way at any moment, National Grid has to warm up some more. In many cases this can take 12 hours of coal or oil burn at a major power station during which time no electricity is generated, and often, once the 12 hours are past, electricity demand turns out lower than forecast, and the stations are shut down without generating anything at all. In
contrast, diesels can start in a few minutes.
On top of that, the low run hours that diesel generators see with Flexitricity are of a similar order to a good-practice test and exercise regime. If a diesel isn’t tested at full power for 50 hours per year, it may not deliver the goods in a real emergency. That is why even diesel generators – properly treated, and not pushed too hard – can contribute to sustainability. We estimate the net effect to be in the range 300-750 tonnes of CO2
per annum for each MW made available.”
Jerwood: "We feel that the real benefit is in the support of the UK’s planned roll-out of wind generation and is something that should be recognised more within the industry. To mitigate the intermittency of wind power, the National Grid is reported to need an increasing STOR requirement which will reach 150 percent of current levels in 2010. So, along with the displacement theory, STOR will in fact play a key role in supporting the ongoing roll-out of noncontrollable renewable generators.”
Booty: Is there feed-in tariff benefit?
Martin: “In principle, yes, but only where the site already qualifies for feed-in tariffs (FITs) or renewables obligation certificates (ROCs). Flexitricity looks for flexibility and the ability to respond to fast-developing needs in the national system. We can’t tell the sun when to shine, so we don’t work directly with solar panels or wind turbines although an increasing number of our clients use these. CHP and hydro stations we can and do work with, and we could work with heat pump systems.”
Jerwood: “STOR requires the active delivery of energy, and hence the controllable renewable generation assets would have to remain dormant until called upon, and thus forego the lucrative FIT generation tariffs (ranging from £45- 300/MWh) which are paid for every hour the asset generates. On top of this, if the site can export this energy, they would receive at least an additional £30/MWh from the scheme. If a 1MW asset generates for 50 percent of the year and attracts the lowest tariff, they would receive
around £200,000 from the generation tariff alone on FIT, in comparison to the higher end of Flexitricity’s stated current STOR market rate of £50,000 per MW per annum.”.
Booty: How is this concept linked into the 'smart grid' idea?
Jerwood: “It’s the central component of the smart grid. Flexitricity makes the consumer responsive to the ebbs and flows of energy in the wider system, which makes it easier to absorb low carbon energy sources while reducing the waste of fossil fuel on back-up power.”
Booty: How much spare capacity is there in the economy?
Martin: “Currently, peak winter electricity demand is just under 60GW. To secure this in 2020, National Grid needs to find an additional 4.5GW of reserve. I expect that all of this can be found from flexible load and generation in the hands of industrial and commercial energy users, and small generator owners. However, harnessing it is a significant challenge; energy users will only participate if they can do so without disruption to
their core business processes.”
Thanet Earth
The massive Thanet Earth greenhouse complex in Kent covers nearly 80 football pitches. It is powered by two large gas-fired CHP generators. These supply heat
and carbon dioxide to the capsicum pepper crop. On average, just under half of this capacity is standing idle at any time, and this spare capacity is made available to Flexitricity.
According to said Pleun van Malkenhorst, production manager of Rainbow Growers, “We need to generate our own power, however, our arrangement with Flexitricity means we are also deriving revenue from the plant, which help towards
our costs. In addition, this helps reduce carbon emissions.
Exhibition centre ExCeL London provides reserve electricity to National Grid within the constraints of normal business operations. The Flexitricity system operates only within pre-agreed limits, which are measured and checked in real time. According to ExCel’s energy manager, Chris Barnes, “When we first started with Flexitricity, we used to watch the generators running every time. Now we just let the generators run, because Flexitricity manages the whole process for us
while we get on with our regular duties. We obviously need to generate our own power. However, our arrangement with Flexitricity means we’re also deriving revenue from the plant, which helps towards our costs.”

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