The Anonymous Widower

We Need More Electricity

Everything we do, seems to need more and more electricity.

We are greening our transport and every electric train, car, bus and truck will need to be charged.

Unless it is hydrogen-powered, in which case we’ll need electricity to split water into hydrogen and oxygen.

Computing and the Internet needs more electricity and is leading to companies putting server farms in countries like Iceland, where there are Gigawatts of low-cost electricity.

We’re also using more energy hungry equipment like air-conditioning and some household appliances.

And then there’s industry, where some processes like metal smelting need lots of electricity.

At least developments like LED lighting and energy harvesting are helping to cut our use.

Filling The Gap

How are we going to fill our increasing energy gap?

Coal is going and rightly so!

A lot of nuclear power stations, which once built don’t create more carbon dioxide, are coming to the end of their lives. But the financial and technical problems of building new ones seem insoluble. Will the 3,200 MW Hinckley Point C ever be built?

That 3,200 MW size says a lot about the gap.

It is the sort of number that renewables, like wind and solar will scarcely make  a dent in.

Unfortunately, geography hasn’t donated us the terrain for the massive hydroelectric schemes , that are the best way to generate loe-carbon electricity.

Almost fifty years ago, I worked briefly for Frederick Snow and Partners, who were promoting a barrage of the River |Severn. I wrote about my experiences in The Severn Barrage and I still believe , that this should be done, especially as if done properly, it would also do a lot to tame the periodic flooding of the River.

The Tilbury Energy Centre

An article in The Times caught my eye last week with the headline of Tilbury Planned As Site Of UK’s Biggest Gas-Fired Power Station.

It said that RWE were going to build a massive 2,500 MW gas-fired power station.

This page on the RWE web site is entitled Tilbury Energy Centre.

This is from that page.

RWE Generation is proposing to submit plans to develop Tilbury Energy Centre at the former Tilbury B Power Station site. The development would include the potential for a Combined Cycle Gas Turbine (CCGT) power station with capacity of up to 2,500 Megawatts, 100 MW of energy storage facility and 300MW of open Cycle Gas Turbines (OCGT). The exact size and range of these technologies will be defined as the project progresses, based on an assessment of environmental impacts, as well as market and commercial factors.

The development consent application will also include a 3km gas pipeline that will connect the proposed plant to the transmission network which runs to the east of the Tilbury power station. The proposed CCGT power station would be located on the coal stock yard at the site of the former power station, but would be physically much smaller than its predecessor (a coal/biomass plant).

I will now look at the various issues.

Carbon Dioxide

But what about all that carbon dioxide that will be produced?

This is the great dilemma of a gas-powered power-station of this size.

But the advantage of natural gas over coal is that it contains several hydrogen atoms, which produce pure water under combustion. The only carbon in natural gas is the one carbon atom in methane, where it is joined to four hydrogen atoms.

Compared to burning coal, burning natural gas creates only forty percent of the carbon dioxide in creating the same amount of energy.

If you look at Drax power station, which is a 3,960 MW station, it produces a lot of carbon dioxide, even though it is now fuelled with a lot of imported biomass.

On the other hand, we could always eat the carbon dioxide.

This document on the Horticultural Development Council web site, is entitled Tomatoes: Guidelines for CO2 enrichment – A Grower Guide.

This and other technologies will be developed for the use of waste carbon-dioxide in the next couple of decades.

The great advantage of a gas-fired power station, is that, unlike coal, there are little or no impurities in the feedstock.

The Site

This Google Map shows the site, to the East of Tilbury Docks.

Note that the site is in the South East corner of the map, with its jetty for coal in the River.

These pictures show the area.

The CCGT power station would be built to the North of the derelict Tilbury B power station. I’ll repeat what RWE have said.

The proposed CCGT power station would be located on the coal stock yard at the site of the former power station, but would be physically much smaller than its predecessor (a coal/biomass plant).

Hopefully, when complete, it will improve the area behind partially Grade II* Listed Tilbury Fort.

Another development in the area is the Lower Thames Crossing, which will pass to the East of the site of the proposed power station. As this would be a tunnel could this offer advantages in the design of electricity and gas connections to the power station.

What Is A CCGT (Combined Cycle Gas Turbine) Power Station?

Combined cycle is described well but in a rather scientific manner in Wikipedia. This is the first paragraph.

In electric power generation a combined cycle is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy, which in turn usually drives electrical generators. The principle is that after completing its cycle (in the first engine), the temperature of the working fluid engine is still high enough that a second subsequent heat engine may extract energy from the waste heat that the first engine produced. By combining these multiple streams of work upon a single mechanical shaft turning an electric generator, the overall net efficiency of the system may be increased by 50–60%. That is, from an overall efficiency of say 34% (in a single cycle) to possibly an overall efficiency of 51% (in a mechanical combination of two cycles) in net Carnot thermodynamic efficiency. This can be done because heat engines are only able to use a portion of the energy their fuel generates (usually less than 50%). In an ordinary (non combined cycle) heat engine the remaining heat (e.g., hot exhaust fumes) from combustion is generally wasted.

Thought of simply, it’s like putting a steam generator on the hot exhaust of your car and using the steam generated to create electricity.

The significant figures are that a single cycle has an efficiency of say 34%, whereas a combined cycle could be possibly as high as 51%.

In a section in the Wikipedia entry called Efficiency of CCGT Plants, this is said.

The most recent[when?] General Electric 9HA can attain 41.5% simple cycle efficiency and 61.4% in combined cycle mode, with a gas turbine output of 397 to 470MW and a combined output of 592MW to 701MW. Its firing temperature is between 2,600 and 2,900 °F (1,430 and 1,590 °C), its overall pressure ratio is 21.8 to 1 and is scheduled to be used by Électricité de France in Bouchain. On April 28, 2016 this plant was certified by Guinness World Records as the worlds most efficient combined cycle power plant at 62.22%. The Chubu Electric’s Nishi-ku, Nagoya power plant 405MW 7HA is expected to have 62% gross combined cycle efficiency.

There is also a section in the Wikipedia entry called Boosting Efficiency, where this is said.

The efficiency of CCGT and GT can be boosted by pre-cooling combustion air. This is practised in hot climates and also has the effect of increasing power output. This is achieved by evaporative cooling of water using a moist matrix placed in front of the turbine, or by using Ice storage air conditioning. The latter has the advantage of greater improvements due to the lower temperatures available. Furthermore, ice storage can be used as a means of load control or load shifting since ice can be made during periods of low power demand and, potentially in the future the anticipated high availability of other resources such as renewables during certain periods.

So is the location of the site by the Thames, important because of all that cold water.

But surely using surplus electricity to create ice, which is then used to improve the efficiency of the power produced from gas is one of those outwardly-bonkers, but elegant ideas, that has a sound scientific and economic case.

It’s not pure storage of electricity as in a battery or at Electric Mountain, but it allows spare renewable energy to be used profitably for electricity generators, consumers and the environment.

The location certainly isn’t short of space and it is close to some of the largest wind-farms in the UK in the Thames Estuary, of which the London Array alone has a capacity of 630 MW.

Wikipedia also has a section on an Integrated solar combined cycle (ISCC), where a CCGT power station is combined with a solar array.

I can’t see RWE building a new CCGT plant without using the latest technology and the highest efficiency.

Surely the higher the efficiency, the  less carbon dioxide is released for a given amount of electricity.

Building A CCGT Power Station

The power station itself is just a big building, where large pieces of machinery can be arranged and connected together to produce electricity.

To get an idea of scale of power stations, think of the original part of Tate Modern in London, which was the turbine hall of the Bankside power station, which generated 300 MW.

Turbines are getting smaller and more powerful, so I won’t speculate on the size of RWE’s proposed 2,500 MW station.

It will also only need a gas pipe in and a cable to connect the station to the grid. There is no need to use trains or trucks to deliver fuel.

Wikipedia has a section entitled Typical Size Of CCGT Plants, which says this.

For large-scale power generation, a typical set would be a 270 MW primary gas turbine coupled to a 130 MW secondary steam turbine, giving a total output of 400 MW. A typical power station might consist of between 1 and 6 such sets.

I feel that this raises interesting questions about the placement of single unit CCGT power stations.

It also means that at somewhere like Tilbury, you can build the units as required in sequence, provided the services are built with the first unit.

So on a large site like Tilbury, the building process can be organised in the best way posible and we might find that the station is expanded later.

RWE say this on their web site.

The exact size and range of these technologies will be defined as the project progresses, based on an assessment of environmental impacts, as well as market and commercial factors.

That sounds like a good plan to me!

100 MW Of Energy Storage At Tilbury

RWE’s plan also includes 100 MW of energy storage, although they say market and commercial factors could change this.

Energy storage is the classic way to bridge shortages in energy, when demand rises suddenly, as cin the classic half-time drinks in the Cup inal.

In Wikipedia’s list of energy storage projects, there are some interesting developments.

The Hornsdale Wind Farm in Australia has the following.

  • 99 wind turbines.
  • A total generating capacity of 315 MW.

Elon Musk is building the world’s largest lithium-ion battery next door with a capacity of 129 MwH

But those energy storage projects aren’t all about lithium-ion batteries.

Several like Electric Mountain in Wales use pumped storage and others use molten salt.

Essex doesn’t have the mountains for the former and probably the geology for the latter.

But the technology gets better all the time, so who knows what technology will be used?

The intriguing idea is the one I mentioned earlier to make ice to cool the air to improve the efficiency of the CCGT power station.

What Is The Difference Between A CCGT (Combined Cycle Gas Turbine) And An OCGT (Open Cycle Gas Turbine) Power Station?

RWE have said that they will provide 300 MW of 300MW of Open Cycle Gas Turbines, so what is the difference.

This page from the MottMacdonald web site gives a useful summary.

OCGT plants are often used for the following applications:

  • Providing a peak lopping capability
  • As a back- up to wind and solar power
  • As phase 1 to generate revenue where phase 2 may be conversion to a CCGT

CCGT plants offer greater efficiency.

I’ve also read elsewhere, that OCGT plants can use a much wider range of fuel. Used cooking oil?

Conclusion

There is a lot more to this than building a 2,500 MW gas-fired power station.

RWE will be flexible and I think we could see a very different mix to the one they have proposed.

 

 

 

 

 

 

July 23, 2017 - Posted by | World | , ,

1 Comment »

  1. […] In We Need More Electricity, I talked about what RWE are doing to create an all-purpose Energy Centre at Tilbury. […]

    Pingback by Electricity Shake-Up Could Save Consumers ‘up to £40bn’ « The Anonymous Widower | July 24, 2017 | Reply


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