Comparative Life Cycle Analysis of

Wave and Tidal Energy Devices

Stuart Walker

Supervised by Dr. Rob Howell

Marine Energy

The UK has marine energy resources equivalent

to 20% of our electricity use*

* Future Marine Energy - Carbon Trust 2006

Tidal• Extract energy from the

tidal stream (in and out)

• Tides are caused by

astronomical movement,

predictable

• Devices resemble an

underwater wind turbine

Wave vs. Tidal

Wave• Extracts energy from the

movement of the waves

• Waves are caused by

wind, unpredictable

• Devices comprise a fixed

base and a moving

component

Project Aim

To compare the lifetime CO2 and

energy performance of Wave and

Tidal marine energy devices

Life Cycle Assessments (LCA):

Wave – Conducted in this project

Tidal – Based on previous work

Tidal Device LCA: SeaGen

SeaGen LCA data was taken

from a study carried out at the

University of Edinburgh.

This study was based on the

test installation in Strangford

Lough, Northern Ireland.

SeaGen Device:

Rated power: 1.2MW

Energy payback: 14 months

CO2 payback: 8 months.

Wave Device LCA: Oyster

Aquamarine Power “Oyster 1”

Test device installed at EMEC in 2008

Rated Power: 315kW

Oyster LCA: Methodology

Transport

Installation

Maintenance

Materials

Decommissioning

OutputOYSTER

MaterialsEnergy and carbon intensities were calculated for major materials

Total Mass = 159 tonnes

Total Energy = 4091 GJ

Total CO2 = 310 tonnes

Material Mass (kg) Carbon (kgCO2) Energy (MJ)

Mild Steel 149,700 264,984 3,652,887

Iron (Ductile) 708 1352 17,700

Iron (Cast) 1058 2020 26,450

Copper 700 2107 29,750

Stainless Steel 6370 39,178 361,202

Plywood 263 213 3942

Materials

Transport

Transport distances of materials and complex components from their

manufacture location to the EMEC site were used to calculate energy, cost and CO2

InstallationOyster installation at EMEC was a complex process:

• Install pipe into hole

• Connect pipe at both ends

• Installation of Containers

• Crane containers into position

• Fix container position

• Connect containers together

• Connect containers

• Drill Pile Holes

• Place piles by crane

• Grout piles in place

• Install flanges onto piles

• Crane Oyster into position

• Installation of Pipeline

• Directionally drill pipeline

Total installation cost:

£2.7 million

MaintenanceAnnual maintenance costs were calculated

based on 4 people travelling 500km by car and ferry, 3 times a year. Spare parts and equipment transport were also included in the spreadsheet.

Decommissioning & RecyclingAs in the SeaGen study, decommissioning data was based on a reversal of relevant installation processes. ICE data was used to calculate the

difference between recycled and primary materials, and the resulting energy and carbon.

Recycling resulted in overall carbon and energy savings, but a net cost of £830,000.

Used Saved

Energy 489 GJ 2,110 GJ

Carbon 36 tonnes 172 tonnes

Cost £864,600 £34,100

OutputBased on a lifetime of 15 years, the Oyster has embodied CO2 of 560 tonnes, embodied energy of 5.4 TJ, and costs

£3.8 million. Output was then calculated.

Using the Oyster power matrix and wave data for the EMEC site it was estimated that the

Oyster would produce 173kW per year.

Oyster LCA

-10,000,000

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

80,000,000

90,000,000

In Out In Out In Out

Energy (MJ) Carbon (kgCO2) Cost (£)

Decomissioning

Maintenance (life)

Installation

Transport

Materials

Lifetime Energy: 76 TJ

Lifetime CO2: 11,800 tonnes

Lifetime Cost: £1.1 million

Oyster vs. SeaGenDue to differences in rated size, Oyster and SeaGen devices were compared in terms of

Energy and CO2 intensity:

And Energy and Carbon payback periods:

Oyster SeaGen Wind Turbine Fossil Fuels

Carbon (gCO2/kWh) 25 15 ~10 400 - 1000

Energy (kJ/kWh) 236 214 ~200

(Months) Oyster SeaGen

Carbon 8 8

Energy 12 14

Further Work• Oyster and SeaGen appear to exhibit good energy

and carbon intensities, and good payback periods.

• Both devices are currently in their infancy so these

are likely to improve further during development.

• Further work is required related to device

survivability and reduce costs.

• Wave device output is unpredictable, so cannot

currently be relied upon to supply grid base load.

Questions?

SLIDES WITHOUT BACKGROUND

Comparative Life Cycle Analysis of

Wave and Tidal Energy Devices

Stuart Walker

Supervised by Dr. Rob Howell

Marine Energy

The UK has marine energy resources equivalent

to 20% of our electricity use*

* Future Marine Energy - Carbon Trust 2006

Tidal• Extract energy from the

tidal stream (in and out)

• Tides are caused by

astronomical movement,

predictable

• Devices resemble an

underwater wind turbine

Wave vs. Tidal

Wave• Extracts energy from the

movement of the waves

• Waves are caused by

wind, unpredictable

• Devices comprise a fixed

base and a moving

component

Project Aim

To compare the lifetime CO2 and

energy performance of Wave and

Tidal marine energy devices

Life Cycle Assessments (LCA):

Wave – Conducted in this project

Tidal – Based on previous work

Tidal Device LCA: SeaGen

SeaGen LCA data was taken

from a study carried out at the

University of Edinburgh.

This study was based on the

test installation in Strangford

Lough, Northern Ireland.

SeaGen Device:

Rated power: 1.2MW

Energy payback: 14 months

CO2 payback: 8 months

Wave Device LCA: Oyster

Aquamarine Power “Oyster 1”

Test device installed at EMEC in 2008

Rated Power: 315kW

Oyster LCA: Methodology

Transport

Installation

Maintenance

Materials

Decommissioning

OutputOYSTER

MaterialsEnergy and carbon intensities were calculated for major materials

Total Mass = 159 tonnes

Total Energy = 4091 GJ

Total CO2 = 310 tonnes

Material Mass (kg) Carbon (kgCO2) Energy (MJ)

Mild Steel 149,700 264,984 3,652,887

Iron (Ductile) 708 1352 17,700

Iron (Cast) 1058 2020 26,450

Copper 700 2107 29,750

Stainless Steel 6370 39,178 361,202

Plywood 263 213 3942

Materials

Transport

Transport distances of materials and complex components from their

manufacture location to the EMEC site were used to calculate energy, cost and CO2

InstallationOyster installation at EMEC was a complex process:

• Install pipe into hole

• Connect pipe at both ends

• Installation of Containers

• Crane containers into position

• Fix container position

• Connect containers together

• Connect containers

• Drill Pile Holes

• Place piles by crane

• Grout piles in place

• Install flanges onto piles

• Crane Oyster into position

• Installation of Pipeline

• Directionally drill pipeline

Total installation cost:

£2.7 million

MaintenanceAnnual maintenance costs were calculated

based on 4 people travelling 500km by car and ferry, 3 times a year. Spare parts and equipment transport were also included in the spreadsheet.

Decommissioning & RecyclingAs in the SeaGen study, decommissioning data was based on a reversal of relevant installation processes. ICE data was used to calculate the

difference between recycled and primary materials, and the resulting energy and carbon.

Recycling resulted in overall carbon and energy savings, but a net cost of £830,000.

Used Saved

Energy 489 GJ 2,110 GJ

Carbon 36 tonnes 172 tonnes

Cost £864,600 £34,100

OutputBased on a lifetime of 15 years, the Oyster has embodied CO2 of 560 tonnes, embodied energy of 5.4 TJ, and costs

£3.8 million. Output was then calculated.

Using the Oyster power matrix and wave data for the EMEC site it was estimated that the

Oyster would produce 173kW per year.

Oyster LCA

-10,000,000

0

10,000,000

20,000,000

30,000,000

40,000,000

50,000,000

60,000,000

70,000,000

80,000,000

90,000,000

In Out In Out In Out

Energy (MJ) Carbon (kgCO2) Cost (£)

Decomissioning

Maintenance (life)

Installation

Transport

Materials

Lifetime Energy: 76 TJ

Lifetime CO2: 11,800 tonnes

Lifetime Cost: £1.1 million

Oyster vs. SeaGenDue to differences in rated size, Oyster and SeaGen devices were compared in terms of

Energy and CO2 intensity:

And Energy and Carbon payback periods:

Oyster SeaGen Wind Turbine Fossil Fuels

Carbon (gCO2/kWh) 25 15 ~10 400 - 1000

Energy (kJ/kWh) 236 214 ~200

(Months) Oyster SeaGen

Carbon 8 8

Energy 12 14

Further Work• Oyster and SeaGen appear to exhibit good energy

and carbon intensities, and good payback periods.

• Both devices are currently in their infancy so these

are likely to improve further during development.

• Further work is required related to device

survivability and reduce costs.

• Wave device output is unpredictable, so cannot

currently be relied upon to supply grid base load.

Questions?