6 Decarbonisation and energy security
benefits
91. It is widely agreed that a tidal barrage in the
Severn estuary has the potential to generate 5% of UK electricity
from a clean, indigenous and renewable source.[203]
The energy security and decarbonisation benefits would be considerable.
This sections explores such benefits in more depth and investigates
how local and environmental concerns should be weighed against
national energy and climate change objectives.
Energy security
92. Hafren Power emphasised the ability of the barrage
to contribute to UK energy security by diversifying the energy
mix and reducing reliance on imported energy. Hafren Power's barrage
would produce 5% of UK electricity, a figure recognised by DECC[204]
and Engineering the Future,[205]
generating 16.5 TWh/year.[206]
Generating on both ebb and flow tides would enable the tidal barrage
to generate for a period of 15.25 hours per day.[207].
Ian Gardner (Director, UKMEA Board, Arup) claimed the Hafren Power
barrage has "a very strong point of applicability and relevance
in a diverse UK market".[208]
Engineering the Future outlined the energy security advantages:
The scheme would add much-needed diversity to
the UK's renewable energy portfolio. Given the barrage's generation
characteristics, it could complement nuclear and wind and reduce
the reliance on imported gas, providing the UK with flexibility
for the future.[209]
On the other hand, the Energy Technologies Institute
noted that alternative low-carbon energy sources exist which could
prove more economical:
A Severn Barrage could provide an important element
of secure energy supply, but there are many alternative ways to
meet the same objective. To decide which is the most attractive
option requires a detailed consideration of the net contribution
of each scheme, their capital and lifetime costs, the economic
benefits they may offer and how each of them might contribute
to the UK energy system.[210]
93. The barrage has the potential to strengthen the
UK energy portfolio - an increasingly urgent objective as the
margin between supply and demand narrows following the closure
of old plant. However, Hafren Power's barrage would not be fully
operational until 2025 at the earliest and will not help address
the more imminent energy gap caused by the closure of coal-fired
plant over the next few years.
"Variable base load power"
94. The predictability of tidal energy, described
as "totally reliable"[211]
by Professor Broyd (Engineering the Future), has advantages over
intermittent sources of low-carbon energy such as wind and solar.
Hafren Power suggests that tidal energy will provide the system
operator with "variable base load power", which the
company suggested will help the grid operator to balance supply
and demand.[212] Accommodating
this tidal power is possible in principle, as illustrated by the
findings of a National Grid study.[213]
On the other hand, there are some drawbacks to tidal power relating
to timing and variability:
The amount of power that would be generated could
be calculated for any period in the future. However, the timing
of energy production would vary with the tides and the amount
of power generated would vary significantly between spring and
neap tides. Even though there are engineering possibilities to
hold back and control water flow through impoundments, there would
be some days every month when electricity was produced at times
when ordinarily demand would be very low.[214]
95. Electricity storage may offer possible solutions
for this in the long-term. However the technology is currently
immature and moreover there is an inevitable loss of energy with
storage. In the immediate future, smart grids and appliances may
therefore offer a more effective way of utilising off-peak generation
through demand management.[215]
Interconnection with other countries could also help to balance
supply with demand. We accept that the a tidal barrage scheme
in the Severn estuary could provide a reliable and predictable
low-carbon electricity supply, which could bring benefits for
energy security. Technological innovations such as smart grids,
interconnection and electricity storage could help to overcome
the challenges associated with tidal energy.
Climate Change Benefits
CARBON SAVINGS
96. Hafren Power stated that the barrage will offer
carbon savings of 7.1 Mt CO2 per year compared to fossil
fuel generation, achieving carbon neutrality after the first 2.1
years of operation.[216]
However, DECC pointed out that the carbon savings will depend
on the type of electricity generation the barrage displaces: for
example, by the time the barrage project comes on-stream, DECC
will not be commissioning unabated coal plant. The Department
calculated that a Cardiff-Weston barrage, if replacing generation
from coal with CCS, would lead to an estimated 219 Mt CO2
savings during its operations, equivalent to 1.8 Mt CO2
per year. DECC estimates for the carbon payback period of a Severn
tidal barrage range from -0.8 years to 7 years, reflecting uncertainties
regarding potential benefits and risks.[217]
A lifecycle assessment of the Cardiff-Weston design carried out
by the University of Bath suggested that "carbon intensity
of the Severn barrage is small in comparison to the National Grid
mix" and, notably, the barrage operation stage rather than
the construction stage was found to be the most carbon intense
due to associated environmental impacts.[218]
We note the disparities in these carbon savings assessments
and the need to take into account a carbon payback period. Carbon
reduction offered by a barrage would nonetheless be considerable.
CONTRIBUTION TO CLIMATE CHANGE TARGETS
97. The 2009 EU Renewable Energy Directive sets a
target for the UK to meet 15% of all energy needs from renewable
sources by 2020. [219]
Although Hafren Power's barrage would not be fully operational
until 2025, the Consortium claim that the EU "will look favourably
on schemes under construction."[220]
The company conceded to the Committee that this was based on an
"understanding" of the process, as opposed to explicit
confirmation from EU institutions. However, the barrage would
be able to contribute to the UK's legally binding 2050 target
to reduce carbon emissions by 80% on 1990 levels, as set out in
the Climate Change Act 2008. In addition, the barrage is likely
to be able to offer some measure of protection against potential
storm surges or other events related to climate change.
Weighing up the arguments
98. Arguments relating to nationally significant
issues such as energy security and climate change benefits must
be weighed against local and environmental concerns. Our oral
evidence sessions drew attention to the importance of striking
the right balance.[221]
Andy Richards (Unite the Union) suggested that the barrage project
should not be prevented from going ahead due to "parochial
future business interests".[222]
However, there is clearly a need to ensure that energy and climate
change solutions are "environmentally acceptable, sensible
and sustainable".[223]
The Minister balanced the arguments as follows:
If there were no alternative to the barrage that
would enable us to meet our 2050 target, then I think the question
that you pose would be at its most acute, i.e. unless we went
down the road of the barrage Britain would miss its 2050 target,
but I am not aware that anyone is seriously saying that is the
case. It is not in our 2050 road map. It is not deemed as yet
to be an essential element of a successful 2050 package and, therefore,
I think, weighing it up, there are better arguments.[224]
99. We conclude that the Hafren Power project
in its current form has not demonstrated sufficient value as a
low-carbon energy source to override regional and environmental
concerns. We agree with the Minister that, at present, the barrage
is not vital to meeting our 2050 carbon targets, for which alternative
pathways exist. On the basis of the evidence available, we further
conclude that the same or similar policy objectives could be delivered
through less environmentally damaging means and possibly at lower
cost.
203 Ev 69, Ev 107, Ev 153; See also DECC, Error! Bookmark not defined.,
October 2010 Back
204
Ev 69 Back
205
Q 113 Back
206
Ev 153 Back
207
Ev 153 Back
208
Q 168 Back
209
Ev 107 Back
210
Ev w85 Back
211
Q 114 Back
212
Ev 153 Back
213
National Grid, Feasibility Study for Connection of Severn Tidal
Generation for Department of Energy and Climate Change, Final
Report, September 2009 Back
214
Ev 107 Back
215
Q 114 Back
216
Ev 153 Back
217
Ev 69. The carbon payback period refers to the number of years
it would take for a barrage to pay back the carbon debt of its
construction and operation. Back
218
Ev w50 Back
219
Directive 2009/28/EC Back
220
Ev 153 Back
221
Q 109 Back
222
Q 51 Back
223
Q 52 [Martin Spray] Back
224
Q 377 Back
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