Tag Archives: Decentralised Energy

April 2013:  There’s been a lot of coverage over the past week over news of an East London scheme to burn so-called ‘fatbergs’. Here’s a run-down over what’s being proposed:

• The developer, 2OC, has signed a 20-year deal worth over £200m with Thames Water to develop a new power station
• 2OC say that a ‘Combined Heat and intelligent Power (CHiP) plant’ will be constructed at Thames Water’s Beckton Sewage Treatment works
• The plant will use  fuels derived from fats, oils and greases (FOGs) – being called ‘fatbergs’ by the press – which build-up in London’s drains [the Sunday Times describes these ‘fatbergs’ as“boulder-sized balls of grease” the worst of which “require “flushers” — clad in protective white suits and shovels — to descend into the bowels of the city to break them up”]
• A Thames Water press release states that the company has committed to provide at least half of the fuel the generator requires – in the form of 30 tonnes a day of FOGs
• Other fuel sources will include oil wastes from food outlets and manufacturers, processors and tallow (animal fats). The company say that there no virgin oils from field or plantation grown crops are to be used
• These FOGS would otherwise be tipped down the drain or dumped in landfill and are responsible for most of the blockages in Thames Water’s 109,000 km of sewers. Removing them costs £1m a month.
• 2OC’s press release states that “The CHiP plant will produce 130 Gigawatt hours (GWh) of renewable electricity a year – enough to run just under 40,000 average sized homes. 75GWh will be purchased by Thames to run its sewage works – and desalination plant (also based at the Beckton site) – and the rest will be sold on to the national grid.”
• Waste Management World states that 19MWe will be generated with the CHP based around a two-stroke marine diesel engine
• Thames Water’s press release provides some additional information on a further novel use of the scheme. The heat output from the CHP scheme will “be used to heat up gas as part of the pressure reduction process at the adjacent Beckton gasworks. The gas pressure has to be dropped to make safe for delivery to homes and businesses. Lowering the pressure of a gas causes a huge drop in temperature, which could freeze and crack pipework. Using waste heat from the engine will reduce the need from gas to be burned to produce the heat currently required to do this job. 20C will also recover some of this thermal energy to generate even more electricity.”
• Back to the 2OC press release which provides some extra info on the last line of the para above: “Additional power is generated from the recovery of thermal energy (provided by heat from the engine)  via a turbo-expander in the gas stream”
• Additional renewable heat will also be made available for any housing schemes nearby
• The Sunday Times article states that “Workers have begun clearing the site, adjacent to the Beckton sewage plant. They must work fast because time is against 2OC and Thames. The facility must be up and running by April 1, 2015, in order to qualify for the giant subsidies it needs to be viable.
  The government guarantees two renewables obligation certificates, a type of green subsidy, for each megawatt hour of power that is generated by experimental technologies. That equates to three times the wholesale electricity price of about £50 per megawatt hour. However, if the Beckton plant comes onstream even one day later than April 1, it will be disqualified.” It’s less to do with it being an ‘experimental technology’ but it being a waste CHP plant which helps quality it for 2 ROCs under the RO.
• The Sunday Times article also considers what the fuel requirement will mean in practice: Importantly, Thames will not be collecting the cooking oil that one would find in a deep- fat fryer. There is already a big market for this. McDonald’s, for example, recycles the oil from its restaurants into biodiesel for its fleet of delivery lorries… At least once a week a Thames lorry will arrive at participating restaurants to collect a fat-laden tray and replace it with it a clean one. Co-ordinating the operation will be a logistical nightmare. The Beckton power plant will need the equivalent of a shipping container’s worth of fat every day.”
• Andrew Mercer, chief executive of 2OC, said:“This is good for us, the environment, Thames Water and its customers. Our renewable power and heat from waste oils and fats is fully sustainable. When Thames doesn’t need our output, it will be made available to the grid meaning that power will be sourced, generated and used in London by Londoners.”
  

Okay:  a lot going on there which is worth going over. What is being proposed is the combustion of these various FOG fuels in a diesel engine to generate electricity. This electrical output from this engine will be directed in the first instance to the sewage treatment works, the Beckton desalination plant (when it needs it – it’s not expected to operate that often) – and also exported to the grid.

The heat from the engine will be captured (as it’s operating in CHP mode) and that will be used to go to the sewage treatment works also, and some is also being proposed to go to local residents via a district heating scheme (of which there is scant detail at the moment). But  some the CHP heat will also go to a Gas Pressure Reduction Station owned by National Grid which is next door to the Beckton sewage treatment works. This is a site where gas is depressurised from the high pressure national gas transmission system, to a lower pressure local distribution system, which can then be fed into homes and businesses. Lowering the pressure of a gas causes a huge drop in temperature, which could freeze and crack pipework, hence heat via a boiler has to be provided on site to help this process (which is currently done). The CHP waste heat will now help fulfil this role, helping reduce the need for gas-burn in the existing boiler.

Last bit: 20C have been exploring for several years now on integrating a device called a turbo expander into the gas pipeline at these pressure reduction station sites.  The expansion of gas at these points from higher to lower pressure allows – with the use of the turbo expander – the generation of electricity. All in all – this  is probably the reason why 2OC are calling this project a ‘Combined Heat and Intelligent Power’ (CHiP) plant!

And did I mention that Thames Water are also installing a 1.5MW wind turbine at the Beckton site also…?!