SMI Conference
Storing Electricity by Storing Gas
2nd February 2012 John Baldwin Managing Director CNG Services Ltd john.baldwin@cngservices.co.uk www.cngservices.co.uk 07831 241217
The Challenge of this Presentation
Aim of this presentation is to address comments such as: “To balance wind generation, we need to store electricity by pumped storage or similar” “Natural gas can have no role in electricity generation”
Storing Electricity by Storing Gas • • • • • • • • • • •
CNG Services Ltd Electricity supply and demand Carbon intensity of supply mix Change in gas demand due to change in wind Flexible CCGT Change in behaviours when its windy Alternatives for storing electricity Converting excess wind generation to natural gas Shallow versus deep salt storage Round trip efficiency using shallow salt Conclusions
CNG SERVICES LTD
CNG Services Ltd • Supports projects to inject biomethane into the gas grid – Developer of Didcot project for Thames Water, SGN and Centrica – Consultant on Adnams Project – Working on 20 further biomethane injection projects in UK
• CNG as a fuel for trucks – Owner of UK’s largest CNG station in Crewe – Developing CNG stations to fuel HGVs
• Supporting development of onshore gas fields and gas storage projects – Ryedale Gas Project – Wingas Saltfleetby – Halite Preesall We are independent from all makers of plant, vehicles, clean-up, compression....we help clients get the best solution for their projects
BG Group Kazakhstan
• In July 2010 we commissioned the first CNG filling station in Kazakhstan • 200 buses ordered for Asian games • CNG is the solution to air quality (no CNG buses in UK due to Bus Service Operators Grant (BSOG) which makes CNG uneconomic)
Most major cities have air quality problems and so make CNG the fuel of choice for buses.....we should have CNG buses in London, we have none
Crewe CNG Station • We re-opened our Crewe CNG filling station in August • Filling 5 CNG dual fuel trucks for GIST/M&S • http://www.youtube.com/watch?v=orxBtoXyjos
Largest grid supplied CNG station in UK – takes gas from 4 bar grid and so uses 20% less electricity compared to 0.2 bar grid
Didcot – UK’s First BtG Project
Digesters
Propane Storage
Gas bag
Propane Injector
Telemetry Energy and quality measurement
CSL – Designer and Project Manager H2S and Siloxane filters
Biogas upgrader
Flow of biogas - 100 m3/hr First gas to grid on 3rd Oct 2010
Electricity Supply and Demand National Grid Scenarios
2020 Targets – How Are We Doing Gone Green or Slow Progression? • Nuclear stations closing down and new ones delayed • Coal plants will be closing down • CCS delayed to post 2015 and may not be viable – projects worldwide being delayed/cancelled • But lots of wind being developed... now 6 GW of generation (though not much production today when it’s cold) • Looks more Slow Progression than Gone Green but let’s assume GG comes through...
Let’s assume NG’s Gone Green Scenario
NG Gone Green - Carbon Intensity of Electricity Supply Mix Emissions intensity pre appliance 600
500 Electricity (Total Grid) Natural Gas 300
Gas Biogas mix
200
Oil Oil Biofuel Mix
100
2050
2045
2040
2035
2030
2025
2020
2015
0 2010
Kg/MWh
400
• Carbon intensity of average electricity generated will drop below that of gas and petrol in the next decade – Assuming new nuclear, CCS, wind etc.
• On this basis it seems straightforward that we should electrify everything but… – Because today it is very cold but not windy – so heat pumps are less than useless
• Anyway, lets assume we have a lot of wind......what implications?
NG say that if there was 30 GW of wind capacity then it is possible to see the following change in gas demand
How to Match the Wind and the CCGT? • First, the basic CCGT has to be efficient • As the EMR reforms are introduced efficiency will be incentivised more than ever • Aiming for 60% efficiency of conversion of gas to electricity
• Next, the CCGT has to be flexible – existing and new ones SSE to Halt U.K. Keadby, Medway Gas-Fired Plants From March 2012-01-31 08:36:13.431 GMT By Catherine Airlie Jan. 31 (Bloomberg) -- SSE Plc will halt two of its natural-gas fed power stations in the U.K. for a “comprehensive program of maintenance to support more flexible operations,” the company said in a statement. It will stop production at its 735-megawatt Keadby and 690- megawatt Medway plants from March 26, according to the statement.
Combined Cycle - Clean but flexible: Rotterdam's Enecogen power plant As well as high efficiency the plant will also be capable of some 200 starts/y, with very high ramp rates and will have features included in Siemens ' FACY (FAst CYcling) package, such as: modified unit co-ordination and balance of plant control system; HRSG standby heating; HRSG fatigue monitoring (FMS); continuous GT load ramp to baseload; high capacity attemperators; ST run up during continuous pressure and temperature increase; high pressure ramp rates with limited HP bypass flow; early closing of HP/IP bypass valves; ST roll off with first steam production; and ST stress controller.
How to Provide Flexible Gas Supplies? • Gas moves slowly through the NTS (around 30 mph) and hence the changes in demand for gas caused by the wind-CCGT interaction cannot easily be met by pipelines moving gas over long distances • NTS line-pack may be able to provide some short term flexibility, but this is limited in volume and duration
• So, gas storage is required, close to where the CCGTs are
NG imagine 30 GW wind capacity in 2020/21 with 1989/90 weather....
So, when its windy, fill the store...
• Key issue then is how much energy used to put gas into store on a windy day and take it out when wind drops? • Before we look at that, what other alternatives do we have to match electricity supply and demand in a 30 GW wind world?
What to do when its windy • • • •
Watch TV Have a cup of tea Make an omelette Charge your car
What NOT to do when its windy • • • •
Watch TV Have a cup of tea Make an omelette Drive your car
There will be an APP for this
In case behaviours don’t change so much, we can store electricity • Have a really big battery • Not invented yet, maybe won’t be
• Have millions of little batteries • Give out a lot of heat, not very efficient, battery life rubbish
• Pump water up hill • 70% efficient if you are lucky
• Compress air • 70% efficient if you are lucky
• Lift a heavy weight • Another pointless thing to do
• Or convert the hydrogen to natural gas….(next slide) • Or, store existing natural gas when its windy and take it out when its not and use CCGTs…(later)
Wind to H2 to natural gas (1) • • • • •
We have invested £30 billion in a gas grid to 90% of customers We have around 50 million appliances that burn natural gas We can store gas in salt cavities So, if we have excess wind, can we turn this into Hydrogen? Yes…..Audi doing it
Wind to H2 to natural gas (2)
• Target is 80% efficiency for electrolysis stage (water to H2) • And 80% for H2 + CO2 to make CH4
Generation at CCGT with gas supplied via NTS CCGT typical size is 800 MW, this looks at 1/800th of such a plant
Gas In 1,000 kWh
Electricity 550 kWh
CCGT
Wasted heat 410 kWh
Parasitic load 10 kWh
Electrical efficiency (Gross) Overall efficiency (Gross)
Transmission Losses 30kWh
= 55.0% = 55.0%
How much energy to store 1,000 kWh when its windy?
We are going to take that gas and inject it into salt cavities such as proposed by Halite at Fleetwood
Shallow v Deep salt? • Salt is ideal for storing gas • Shallow salt near Fleetwood area • Deep salt in East Yorkshire • They have different characteristics
Shallow v Deep salt? To move 1 Million m3 into and out of store
• Shallow salt is more like gas pipeline as its pressure is low • Deep salt is like a depleted gas field – needs much more energy to inject gas into the store and to take it out
How much energy is used to compress it into store and take it out? • 1,000 kWh = 969 therms = 97,000 SCF = 2,750 M = 0.027 MCM 1 MCM contains 37 MWh of gas • To put 1 MCM into a SHALLOW SALT store when its windy and take it out again when it is not requires 1.2 MWh of energy = around 3.3% of the energy
• So, round trip efficiency is 96.7% - a lot better than doing things that you do not want to do....
Conclusions Aim of this presentation is to address comments such as:
“To balance wind generation, we need to store electricity by pumped storage or similar” Store natural gas and use with flexible CCGT “Natural gas can have no role in electricity generation” It is the main long term strategic partner for intermittent wind and we can make it renewably • The combination of flexible CCGT and Shallow Salt storage provides the lowest energy (and hence lowest CO2) way to balance electricity supply and demand • The EMR process should send the appropriate signals to ensure that such Shallow Salt is developed by 2020 in order to provide this capability • If there is every surplus wind/nuclear/solar etc above what the storageCCGT combination can handle, best option likely to be to make the excess electricity into CH4 and distribute via gas grid