Memorandum submitted by Mr Paul Spare
The UK is an advanced industrial economy wherein
a reliable electricity supply is as fundamental to prosperity
and social welfare as are food or water. Electricity is currently
supplied with about 99.97% reliability,which is the level of service
that society and industry expect to continue. Similarly, the supplies
of oil and gas are extremely reliable. For any novel technology
to supplant these existing systems by normal commercial means,
it must achieve the same performance more economically, or provide
better performance for the same cost. If these criteria are not
met, statutory measures will almost certainly be required to change
behaviour, especially at the start, when the economics of replacement
system are most unfavourable. The remainder of this paper examines
the problems associated with "non-carbon" replacements
for existing energy supplies.
2. THE OPTIONS
There appear to be only two main options for
the non-carbon (ie no coal, gas or oil) fuel economy:
(1) Use electricity generated from sources
contributing little or no CO2 in conjunction with hydrogen.
(The hydrogen can be either burned to generate heat or used in
fuel cells to generate electricity.)
(2) Use electricity generated from sources
contributing little or no CO2 + battery storage devices.
This analysis is concerned only with Option
3. CURRENT ENERGY
There are two stages to reviewing the implications
of the "non-carbon" (hydrogen) economy. Firstly, identifying
the power supplies that would have to become hydrogen-based and
secondly identifying/providing the resources and structures to
accomplish the change. This latter point is introduced at an early
stage, as it is demonstrated below that hydrogen-based economies
will require a massive increase in electricity generation, over
present levels. The scale of the problem may not be apparent when
the use of hydrogen is viewed in sweeping "policy" terms.
Various current carbon-intensive technologies
could be replaced in whole or in part. The table below shows some
energy consumption data in the UK from recent DTI statistics.
The fuels are used for many purposes and the thermo-mechanical
efficiency achieved varies over a wide range, eg transport 25%,
heating 75% and electricity production 40%.
|Energy source/Fuel||Annual Consumption
||Consumption in Mtoe
|Oil||76 million tons||76
|Coal||64.5 million tons
|Nuclear electricity||Approx 83 TWh
|Nuclear Imports||11 TWh
|Hydro + others||12 TWh
Consider the replacement of half of the three most important
fuels, shown above, by hydrogen. In round terms, energy equivalent
to 100 mtoe would be needed annually. If the same thermo-mechanical
efficiency is achieved then, allowing for the higher calorific
value of hydrogen compared with hydrocarbons (2.5:1), as much
as 40 million tons of hydrogen would be required each year. This
implies many thousand times the current annual rate of production.
This illustrates the scale of the challenge. The capital investment,
planning, construction and environmental issues involved may not
be apparent when considering broad political gestures. Changes
of such an order generally take several decades to accomplish,
even when driven by favourable economics; ie steam replacing sail
or the internal combustion engine replacing the steam engine.
For the conversion to the low-carbon society, the economic pointers
may not be favourable for 10 or 20 years.
4. POTENTIAL FOR
Consider replacing the fuel supply for certain vehicle users.
This transition would involve four elements.
Production of the hydrogen.
Delivery to point of use.
Storage (not considered here).
The same technical approach can be taken to other fuel supplies.
This analysis follows a well-understood methodology. I am indebted
to the Alistair Miller and Romney Duffey of Atomic Energy of Canada
Ltd (AECL) for the calculations for vehicle fuel.
By the terms of an EU agreement with car manufacturers, new
cars are expected to emit 140 g CO2/km by 2008 and
so it would be reasonable to use this as representative for the
UK fleet by 2020. This is equivalent to 6.2 L/100 km. Or -27%
fuel efficiency. The full energy content of motor spirit is estimated
as 9.1 kWh/L; so 2.45 kWh/L would be delivered energy. The alternative
of water electrolysis (70% efficient as compressed hydrogen energy)
followed by a fuel cell (50% efficient in net output) has an overall
efficiency of 35%. To deliver 2.45 kWh of drive energy by this
electrolysis/fuel cell route will require 7.0 kWh of electricity
to the electrolysis cell. This is equivalent of one litre of motor
spirit in terms of delivered, propulsive energy.
The DTI report projects motor spirit consumption only to
2010 but the proportion is reasonably steady at about 38-39% within
a rising total that is projected to reach around 65 Mtoe in 2010
and would, by simple projection, be around 75 Mtoe by 2020. Hence
motor spirit consumption of about 29 Mtoe is projected for 2020.
Taking the density of sweet crude as 0.85, 29 Mtoe become 34 x
106 m3. Assume that about 95% of this by volume is converted into
product, including motor spirit. So estimated total consumption
in 2020 would be 32 x 109 L.
Based on fuel-cell powered vehicles in significant numbers
emerging about 2010 and a turnover of the light vehicle fleet
of around 5%/a, it appears reasonable to project that about 20%
of the light vehicle fleet (ie vehicles fuelled by motor spirit)
will be using fuel cells by 2020. Then 5.6 x 109 litres of motor
spirit (5.1 Mtoe of oil) could be displaced by electricity. If
generated by nuclear or other power source with negligible CO2
emissions, emissions would be reduced by 4.3 MtC. Electricity
for this displacement would be 43 TWh/a, the output of 5.5 GW
of electric capacity operating at 90% efficiency. This is slightly
less than the output of five Sizewell B reactors, or eight 700-MW
Advance CANDU (ACR) reactors.
There are two options for distribution:
Produce the hydrogen in a small number of regional
electrolysis plants and distribute to users.
Distribute electricity to the local communities
for electrolysis plants to make hydrogen locally.
The former may appear at first site to be the more expensive,
since an entirely new distribution system will be needed. However,
the second would need substantial investment in the electricity
distribution network. The present system will not be capable everywhere
of carrying the extra energy supplies on top of the existing demand.
It will require substantial reinforcement with commensurate investments.
6. REPLACEMENT OF
Gas is used in a ratio of about 70:30 for direct heating/electricity
generation. Consider the replacement of the 70% component used
for direct home heating/cooking, industrial heating and commercial
One option would be for the heating function of gas to be
replaced by nuclear generated electricity, amounting to 700 TWh.
The distribution of electricity and its use for heating should
have an efficiency of 90%, compared with 75% for direct combustion
of gas. About 600 TWh of electricity would therefore be needed.
That can be achieved by about 75 GW of nuclear plant operating
at 90% availability. This implies about 50 new nuclear plants
such as Sizewell. Again however, the HV super grid and distribution
network would have to be strengtheneddoubled or trebled
in power handling capacityto provide power to consumers.
The second option is to replace natural gas by hydrogen +fuel
cells, with hydrogen distributed via the (otherwise redundant)
gas pipe work infrastructure rather than direct power through
the electricity supply grid. In this case, more electricity would
be required to compensate for the lower efficiency of hydrogen
production/fuel cells, compared with heating directly by electricity.
As quoted above this efficiency may be only about 35%. In which
case the generation of electricity would have to be increased
by 90:35 is about a factor of 2.5 times. However, the change would
necessitate over 100 new reactors. An increase of this magnitude
is probably not feasible, because of one or more of the following
beyond the capacity of the available coastal and
beyond the output capacity of fuel manufacturing
beyond the capacity of the construction contractors.
Such obstacles almost certainly rule out this option. They
also serve to illustrate in the clearest possible terms the importance
of rationing the remaining stocks of natural gas. Proposals (which
I supported) to debar the use of natural gas for electricity generation
were not successful. The consequences of that decision will be
visited upon us in the next few years, if the supplies planned
to be imported from eastern Europe, do not materialise. Nuclear
plants would have to be constructed to replace CCGT plants, but
it could still prove impossible to meet energy demands.
Utilising the gas transmission network should be technically
feasible, being akin to reversing the conversion from Towns Gas
to Natural Gas that was accomplished about 30 years ago. It would
also avoid the need to triple or quadruple the power handling
capacity of the typical domestic electric supply system that would
be needed if home heating is supplied by electricity rather than
7. POWER SOURCES
Nuclear-generated electricity is a particularly attractive
source for any hydrogen production, since the reactors can meet
the peaks of daytime electric demand and produce hydrogen in the
broad periods of reduced demand. A small contribution from renewable
sources would not be excluded, but the scale of increased energy
demand is probably two orders of magnitude beyond their most optimistic
14 October 2002