Combining coal and renewables

Dr Stephen Mills

IEA Clean Coal Centre,

London

International Power Summit, Munich,

19-21 February 2014

Introduction and content

• Introduction and background

• Reasons for coupling coal use with REs

• Growing level of renewables and their impacts

(with particular emphasis on biomass and wind)

• Gasification and co-gasification

• Hybrid energy-producing schemes

• Summary

Global energy demand and supply

Coal will still be used widely

• biggest use now is for

electricity generation

By 2040, world population of ~9 billion

Global energy demand 30% higher than now

Largest individual proven national coal

reserves (Mt)

electricity generation

(42% of world’s electricity)

• provides >30% of global

primary energy

• global coal consumption has

increased for 12 successive

years

• production has soared in some

non-OECD countries

0

50,000

100,000

150,000

200,000

250,000

Global increase in renewable energy

Wind:

• latest additions of ~45 GW/y

• global wind capacity now >280 GW

• around 70 countries have >10 MW of

capacity

• ten biggest players = 87% of total

capacity

• includes China, the USA, India,

Germany, UK, Canada

Biomass:

• can take many forms

• uptake for energy production

increasing in many countries

• often environmental and economic

considerations

• frequently supported by incentives

0

200

400

600

800

Mtoe

EU 27 gross energy consumption

Why the growth in renewable energies?

• depletion of energy resources

• diversification of sources

• possible climate change linked to the use of

fossil fuels

Perceived advantages of VREs

• capital costs high, but operating costs may be low

• ‘fuel’ costs may be negligible or even zero

• no pollutant emissions from day-to-day operation

• similarly, no direct CO2 emissions

Intermittent renewable energies

Solar power – USA Wind power - UK

The rise of intermittent renewables

• the use of such technologies will

increase further - particularly wind

and solar power

• increasingly, they will form part of

networks or grids that also include

thermal plants (coal and gas)thermal plants (coal and gas)

• because they operate in a different

manner, their variable output can

have a number of impacts on thermal

plants

Impacts on other power plants

When input from renewables is high, thermal

stations may be expected to operate at part load

or cycle

Hard coal Lignite Natural gas

Combining coal and renewables

Biomass, wind, solar, etc.

- why bother?

- what are the incentives?

Energy production using combinations

of coal and renewables

mmm

Wind power

• Forest residues

� thinning operations

� logging

� fire prevention

� downstream processing

Biomass

Various ways to combine the use of coal, biomass

and intermittent renewables have been proposed

� downstream processing

• Energy crops

Advantages and disadvantages

of biomass use

Pros:

• use unwanted wastes

• minimises landfill

• reduce fossil fuel use

• extend life of fossil fuel reserves

• reduce conventional emissions

• reduce CO2

Cons:

• can be expensive to harvest and produce

• may tie up land and other resources

• seasonal limitations

• some residues retained in situ for ecological reasons

• low CV - may need large amounts

• physical properties – grinding, pulverising

• chemical properties (alkalis, chlorine)

The World’s forests

Where and how much?(1000 ha)

• Africa 675,000

• Asia 593,000

• Europe 1,005,000

• Americas 1,570,000

Total >4,000,000

Top five most forested countries:

Russian Federation > Brazil > Canada > USA > China

Logging operations

Gasification

• versatile and well proven for power generation,

chemicals, fuels, and fertilisers

• virtually any carbon-based material can be

gasified

• coal most widely used; but also some biomass• coal most widely used; but also some biomass

• different gasifiers - many variants available:

� entrained flow

� fluidised bed

� fixed bed systems

Coal and biomass gasifiers

Typical biomass gasifiers much smaller than coal

Coal Biomass

2500 - 15,000 t/d 25 - 200 t/d

Air- or oxygen-

blown

Mainly air-blown

Great Plains, USA JY biomass gasifier, China

Coal/biomass co-gasification

Advantages

Coal Biomass Co-gasification

High energy content May be low cost waste or

residue

Large coal gasifiers – economies of scale

- high efficiency, better economics

Widely available Lower emissions Allows biomass access to well-

established processes

Large reserves High availability in some

countries

Smooths out seasonal biomass

availability

Less prone to price

fluctuations

Reduces impacts of variations in biomass

properties

Usually costs less than Reduces coal plant emissions; possibly Usually costs less than

biomass

Reduces coal plant emissions; possibly

credits for the use of renewable fuel

Well proven in large-

scale processes

Some biomass catalyses coal reactions;

synergetic effects observed

Disadvantages

Production-related

impacts

Lower energy content Storing, feeding, blending arrangements

may be more complex

Conventional pollutant

emissions

Variable properties

CO2 emissions Harvesting, transport and

pre-treatment costs

Seasonal availability

Tar, alkali issues

Co-gasification projects

IGCC power plants

Plant Capacity (MWe) Gasifier Biomass used

Buggenum,

Netherlands

284 Shell Dried sewage sludge, chicken litter,

sawdust

ELCOGAS,

Spain

335 Krupps-

Koppers

PRENFLO

Olive wastes, almond shells, waste wood,

vineyard wastes, MBM

Polk plant, USA 250 GE Bahia grass, eucalyptus

Chemicals production

Berrenrath, Methanol HTW fluidised MSW, dried sewage sludge, loaded cokesBerrenrath,

Germany

Methanol HTW fluidised

bed

MSW, dried sewage sludge, loaded cokes

Schwarze

Pumpe,

Germany

Methanol Combination

of BGL, FDV,

GSP

Demolition wood, sewage sludge,

plastics, MSW

Sasol, S. Africa Various Sasol-Lurgi Bark, wood pulp/bark

ZAK + PKE,

Poland

300 MWe + MeOH,

chemicals

na na

The Willem Alexander IGCC plant,

The Netherlands

Dried sewage sludge

Sawdust

Chicken

litter

Combined gasification and renewable

energy concepts

Organisation Technologies proposed Status

NREL, USA Gasification/

co-gasification +

electrolysis (wind)

Various studies under way. Concepts include:

• combining wind power and biomass gasification

• combining biomass gasification and electrolysis

• combining coal and biomass co-gasification

Several gasification-based hybrid systems being examined

NETL, USA Coal gasification +

electrolysis (wind)

Systems to produce SNG, electricity and biodiesel.

3000 t/d plant proposed.

Unconverted coal from gasifier fed to oxy-combustor

CRL Energy,

New

Zealand

Coal/biomass

co-gasification +

electrolysis (wind)

Syngas could be used to produce low-carbon FT chemicals, synfuels

Oxygen from electrolysis fed to gasifierZealand electrolysis (wind)

Oxygen from electrolysis fed to gasifier

Hydrogen - enrich product gas, stored, transport fuel, fuel cells

Leighty

Foundn, USA

Coal/bio. co-gasification

+ electrolysis (wind)

Oxygen from electrolysis fed to gasifier

Univ. Lund,

Sweden

Biomass (wood) gasifier

+ electrolysis (wind)

Oxygen from electrolysis fed to gasifier

Elsam/DONG

Denmark

Biomass gasification +

electrolysis (wind, solar)

Various co-generation concepts to produce power, heat, transport

fuels examined.

Hydrogen added to syngas. Oxygen for biomass gasification

Lausanne,

Switzerland

Wood gasification +

electrolysis

Several processes examined for SNG production

China Various: Gasification +

electrolysis (wind)

Oxygen from electrolysis fed to gasifier.

Hydrogen fed to syngas.

Mainly for SNG, methanol, ethylene glycol production

Water electrolysis

Electrolysis is a means for separating water into gaseous hydrogen and oxygen

Only inputs are feed water and low voltage direct current

Hydrogen and oxygen production by

water electrolysis

Several different types of electrolyser are available commercially:

• proton exchange or polymer electrolyte membrane (PEM) electrolysers

• alkaline electrolysers

• solid oxide electrolysers

• electrolyser efficiencies between 56 and 73%, but RD&D is

improving this;

• electricity supply from any source but to be viable, must be • electricity supply from any source but to be viable, must be

low cost;

• despite intermittent output, wind currently the lowest-cost

renewable.

Several factors determine the cost of hydrogen and oxygen:

• capital cost of the electrolysis plant

• its overall efficiency

• the cost of the electricity input

Large scale electrolysis

Examples of commercial scale electrolysis facilities

NEL Hydrogen Technologies

Lurgi electrolyser

E.ON Power-to-Gas (P2G) project

Electrolysers

hydrogen

oxygen

Natural gas grid

Possible uses for gases produced

Hydrogen

Syngas Fuel cells Transport fuel Gas turbines

Hydrogen

Oxygen

Industrial applications Coal/biomass gasifier Oxyfuel combustion

Hybrid systems incorporating renewables

USA Several studies of hybrid systems for SNG, electricity, transport fuels.

Includes gasification and electrolysis, and coal/biomass co-gasification

with CCS

Denmark REtrol Vision (REnewable energy + petrol) - cogeneration + transport fuels.

Biomass gasification, electricity from renewables, water electrolysis,

+ CO2 from post-combustion capture

Sweden Biomass gasification + wind power. Oxygen from electrolysis fed to gasifier

Examples of studies – based on coal, biomass, coal + biomass

Sweden Biomass gasification + wind power. Oxygen from electrolysis fed to gasifier

New

Zealand

CRL Energy – coal/biomass co-gasification + wind energy for electrolysis.

Oxygen fed to gasifier; hydrogen to enrich syngas.

Production of FT liquids and other products

China Various studies combining coal gasification + renewables.

Wind energy for electrolysis. Oxygen fed to gasifier.

Hydrogen used to enrich syngas. Syngas used for methanol production

Switzer-

land

Biomass gasification + electrolysis. Oxygen fed to gasifer.

Hydrogen used to enrich SNG then fed into natural gas grid

Germany RWE Power-to-gas project (Niederaussem) will couple wind electricity,

Siemens PEM electrolyser, CO2 from power plant flue gas, to produce SNG

APS demonstration plant, New Mexico, USA

• H2 and O2 from wind-

powered electrolysis

• H2 to gasify >3000 t/d of

coal

• produces SNG, fed to grid • produces SNG, fed to grid

or power plant

• unconverted coal fed to

oxygen combustor to

generate 41 MWe

• 90% CO2 capture from

power production - fed to

an algae farm for

biodiesel production

Summary 1

• many schemes proposed, but fossil fuels will remain vital

- combine these with renewables such as biomass and wind

Growing global population and rapidly rising energy demand

Incentives to develop novel energy-producing systems

- combine these with renewables such as biomass and wind

• each individual power source has its own pros and cons

- but combining these may overcome many shortcomings

• to be a runner, systems need to be practical, economically

viable, and environmentally benign

Summary 2

Gasification • both coal and biomass gasified individually

• many technology variants available for each

Coal/biomass

co-gasfn.

• can provide advantages; overcome some problems

• can be environmentally and economically beneficial

• possibilities for producing a range of different products

(SNG, chemicals, transport fuels)

• a number of routes being pursued

Gasification

+ renewables

combinations

• examined some of the more promising concepts being

developed

• particular emphasis on co-gasification coupled with wind-

powered electrolysis (H , O )powered electrolysis (H2, O2)

• many projects still at early stage in their development

• some propose to incorporate CCS

Co-gasification + renewables

Some further advanced - some parts well established (co-gas) – other parts

being trialled (commercial demo of H2 production from wind, and advanced

electrolysers).

If economics can be made to work, several concepts that combine coal,

biomass and intermittent renewables look promising.

Thank you for your attention

Dr Stephen Mills

IEA Clean Coal Centre, LondonIEA Clean Coal Centre, London

Email: Steve.Mills@iea-coal.org.uk