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1 December 2008
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Variable renewables
Wind power
Solar Photovoltaic
Tidal and wave
generation
Constant
renewables
Hydroelectricity
Biomass
electricity
Geothermal
electricity
Biomass gas
Enhancing the
value of waste
Conclusion
Further reading
To date, renewable energy has not been given a
high priority in Cyprus. The current implementation of renewable energies is
quasi-zero, with the exception of solar water heating. The latter is so
commonplace that little attention need be made (see the essays on
Houses and Water).
Parliament has paid lip service by passing a law offering certain subsidies
for some kinds of renewable electricity generation but, at the time of
writing, these have not actually been made available because of bureaucratic
procedures - even after two years. The Electricity Authority of Cyprus (EAC)
has, in the meanwhile, been collecting a small tax (0.22 c/kWh, about 2.5%)
on electrical consumption, ostensibly to fund these subsidies.
It would appear that anyone installing an
approved system will be able to obtain up to a direct 40 per cent subsidy on
the capital cost, exemption from 15 per cent VAT (making 55 per cent, in
all) and, if there is a surplus of electricity fed back to the grid, this
will be purchased at 20.5 c/kWh, which is roughly 1½
times the selling price (this data is subject to correction as fuel
prices vary).
From my own experience, I know that obtaining
the subsidies is a discouraging and lengthy procedure. The initial part of
it, obtaining approval from the EAC, is easy, rapid and straightforward. The
next part is submitting an application to the Ministry. It would appear that
the latter is as obstructive as possible, despite the application form
(several pages, only in Greek) being filled in completely and sent along
with all the required documents. The first ploy is to do nothing apparent
for six months. If, after that time, you start to enquire what is happening,
you are then asked for further documents that were not requested initially.
When these are submitted, the process restarts and one has another several
months wait. The dossier is then sent to the Land Registry to obtain
planning permission for the installation - and everyone knows how fast the
Land Registry works! Eventually, I suppose, permission to install is
granted. However, before you can hope to see any financial return from the
government or the EAC, I imagine that all the bureaucrats from every quarter
will have to inspect the installation and woe betide you if you have used an
M8 screw when the plan says M6! With a great deal of luck, you may get a
cheque for the 55 percent on the capital cost, probably several months
later. If you think that this sounds cynical, I have experienced it myself
up to about half-way through the procedure, when I decided to renounce it.
In the meantime, I estimate the EAC has raked in over €10
million with the levy, enough to pay for the capital subsidy of somewhere
about 1,000 photovoltaic installations of 3 kW each, representing about 1
per cent of the average generation on the island during daylight hours. It
is doubtful whether the number of applications for PV installations is
one-quarter this figure. If I were really cynical, I might even go so far as to say
that the authorities were sitting on the money they have collected from us,
the consumers, to pocket the interest for other purposes. However, my
cynicism is not limitless.
These are defined as energy that cannot be
generated at a constant level. Some examples are tidal, solar and wind
power. These are sometimes called intermittent sources, but I prefer the
term "variable" over "intermittent", because the latter implies an "all or
nothing" energy generation, whereas the output more commonly varies from
nothing to full output with every intermediate level possible. It should be
noted that it is essential that constant power supplies must be available to
cover the maximum demands, so that variable renewables can only serve to
allow conventional power stations to be "eased off", thereby reducing fuel
consumption. Good weather forecasting is a sine qua non of useful
exploitation of variable supplies, so that the constant requirements can be
foreseen and the plant brought up to speed accordingly.
It must be noted that there is a limit to the
amount of variable energy that a power grid can handle at any one time.
Above that limit of 18 - 20 per cent, experience in other countries has
shown that the whole grid system may become unstable, leading to black-outs.
In some countries in higher latitudes, wind
generation, both offshore and onshore, has been well implemented with
further expansion planned. Cyprus is not very suitable for large scale wind
farms. Generally speaking, wind generators have a rated output with wind
speeds of about 16 - 20 m.s-1 and the output drops to about half
at 10 m.s-1 and one-quarter at 7 m.s-1. The annual
average wind speed in most places on the island is within the range of 2 - 5
m.s-1 with the highest values of about 7 m.s-1 because
of katabatic winds on the southern slopes of the Troodos massif. This means
that wind turbines could never operate efficiently in this country. This is
exacerbated by the fact that these machines shut down when the wind speed
exceeds about 20 m.s-1 such as may happen during winter gales.
The graph shows the
empirically measured output from a typical wind generator in the
megawatt range. It is clearly non-linear and gives full output
only over a limited range of sustained high wind speeds near to
full gale force of, say, 15-20 m/s. If the wind drops to an
average of 10 m/s, the output drops to only about 40% of the
turbine's rated output, yet 10 m/s is still quite a powerful
wind (22 mph, 35 km/h, Fresh Breeze on the Beaufort scale).
Above about 20 m/s, the blades are feathered and brakes applied
to prevent damage.
This graph shows the
yearly average wind speed at a land-based location, considered
as very favourable for the exploitation of wind energy
(North-east Scotland). If we integrate the two charts above, we
obtain a total weighted turbine output of about 37% of the rated
turbine output:
It is emphasised
that the location in the above example is considered as very
favourable with strong sustained winds. Strong gusts with a low
average wind speed is more common in many locations and is not
so favourable. To illustrate this point, this is a random 24
hour wind speed chart from my
weather station,
in Mosfiloti, in a location
sheltered by surrounding hills:
The red line is the
gust speed in m/s, the blue line is the 2-minute average and the
green line is the minimum. The blue line is missing between
about 1930 and 0820 (computer switched off, average not
calculated). The point I wish to make is that, if we look to the
extreme right of the graph, we can see the wind is gusting up to
10 m/s, but frequently drops to zero, with low averages. This
gustiness is useless for wind generation. On the other hand,
between 0500 and 0700, the gusts are lower, up to about 5-6 m/s,
but the minimum wind speed is between 2 to 4 m/s. If this were
in a more exposed location with, say, double these wind speeds,
the latter period would be reasonable for electricity
generation, but it would be difficult to amortise a turbine
under these conditions with a couple of hours generation at less
than half capacity in a day!.
According to a letter by Bill Hyde,
published in Engineering & Technology magazine (Vol 3, no. 20, November
2008), nothing is generated at wind speeds below 4 m.s-1 and
he goes on to cite that Germany has 23,044 MW capacity of wind turbines
installed. Between 2100 on 3 November 2008 and 2359 on 5 November, it
produced less than 1000 MW (<4.35 of capacity) with a low 20 MW (0.09%)
at the peak consumption time of 1200 on 4 November. This illustrates the
need for wind (and solar) to have 100% fixed backup available,
considering that Germany is a much windier country than Cyprus. He
finishes "Customers don't like blackouts - especially the home dialysis
people". In fact, he points out a source of data on the German
electricity output from wind at
this site,
with graphs of weekly production. The sample below shows that periods of
day at <10% of capacity are not uncommon and the peak production is at
about 42% of capacity. I haven't integrated the curve, but it would see,
by eye, that the average is less than 20% of capacity over that week.
Other data shows typical output over the summer months at about 10%
capacity.
There is a particular problem with wind
generation in Cyprus. It would be nice if the turbines produced their peak
power to correspond with peak electricity demand. Unfortunately, this can
never happen. Peak demand occurs in the hottest weather, when temperatures
exceed, say, 35°C, because of air-conditioning. Throughout the summer, the
meteorological situation is that a series of high pressures pass over the
island from about early June to mid-September and this is when there is a
minimum of wind.
It is estimated that the average cost of
on-shore wind-generated electricity would be over twice that of
fossil-fuelled generation under these conditions. Off-shore installations
would be even less efficient.
There is a project to install a small wind farm
in the Kouris Dam region. The details are unknown, but its rated capacity is
unlikely to exceed about 5 per cent of peak demand. Some concern has been
raised about this project because the lake has become a habitat for many
species of wild birds, especially migrant waders. It is possible that this
region will be designated an IBA (Important Bird Area) by the Game Fund and
Birdlife Cyprus, under EU rules. It is feared that the windmills may kill
migrating birds, some of which are rare and protected species. It is perhaps
not appreciated that a 2 MW wind turbine may have blades of 65 m diameter on
a mast of 100 m height. The tips of the blades may rotate at speeds of 100
km/h or more, so that large birds may not have a opportunity to avoid them
if the blades interrupt their flight path. The blades themselves can
also be damaged if the bird is of the size of a duck or more. This has been
a problem in the USA, especially with raptors (see the essay on
Wildlife).
This is perhaps the ideal variable renewable
energy source for Cyprus, except for its capital outlay. Cyprus has well
over 2,500 hours of "useful" sunshine per year, so that a 3 - 4 kW system
(size which will fit on a typical south-facing villa roof) will generate a
theoretical 7.5 - 10 MWh. However, be warned, you will never reach this
theoretical limit because the efficiency of the solar panels drops at
temperatures above 25°C; it would be wise to budget for 5 - 7.5 MWh
respectively. If one were to buy a PV system at its full price and not sell
any surplus electricity generated, the payback period would probably exceed
the lifetime of the system. With the subsidies and the EAC buy-back price,
assuming you are willing to go through the rigmarole of making the
application, an average household would have a payback period of 8 - 10
years, after which it will become profitable (subject to reserves on the
final conditions of subsidies). There is a risk that if oil prices exceed
about $220/barrel, the EAC buy-back price will be less than the cost of
buying a kWh from them.
The real cost of generating solar
PV electricity is very high, typically 35 - 50 c/kWh. However,
it can make a real contribution to smoothing out peak demands
because it will be reasonably productive at the time when
air-conditioning units and chillers would be working hardest.
This alone makes it interesting, despite the high cost and the
surtax burden on the ordinary electricity consumer.
Granted that the notion is not practical, but
if every house that has a solar water heater also had 3 kW of solar panels,
then the peak power requirements of the whole of the EAC supply could be met
on sunny days. In practice, to ensure grid stability, only one house in five
could be thus equipped, but that alone could save over 20 per cent of the
fuel used by the EAC.
It has been said that one form of
tidal electricity generation is like wind generation under
water. Where this analogy fails is that tides are largely
predictable, wind is not. However, it should be stated that
there are four periods per day when tide generation does not and
can not work; as the tide turns, hence it being classed as
variable, even though it is predictable.
Another form uses a barrage across
a tidal estuary or bay, while a third type uses the pressure
differentials in a concrete caisson.
Unfortunately, the tides in Cyprus
are insufficient to be able to be harnessed.
Wave generation is a possibility
when the average height of the waves (crest to dip) exceeds 1
metre. I have not studied this possibility, but I instinctively
believe that it is not likely to be a viable option on this
island. The "best" waves for this are oceanic swells, but local
wind-driven waves would also work. However, as these are
dependent on wind, it is probable that the same conditions as in
the paragraph on wind generation would probably apply.
Hydroelectric generation is the mainstay in
countries, like Norway, Switzerland and Austria, where there are large
glaciers. The water from the summer melt-off is collected in large dams, at
altitude, and penstocks lead the water to pressure-operated turbines in the
valleys. Alternatively, large dams across rivers, such as the Three Gorges
Dam in China, can turn flow-operated turbines. Both types are
environmentally disputed for several reasons and large projects are nowadays
very severely criticised. Both types are also potentially dangerous to
downstream life if, for any reason, the dam should burst and this does
occasionally happen, despite the best efforts of civil engineers. This is
unlikely to happen in Cyprus, because of the lack of perennial rivers.
There is a variant of hydroelectric
generation which could possibly have some future relevance to
counter the undesirable effects of variable renewables. Imagine two lakes of equal size, say,
similar to that of one of the larger dams, but separated in altitude by 300
- 500 m. During the night, when there is a surplus of power generating
capacity, water is pumped up from the lower to the higher. At peak demand
time or when variable renewables have a low output (e.g., no wind and a
cloudy day), the water in the upper reservoir is made to flow down to the
lower lake, generating hydroelectricity. This method is the only useful way
of "storing electricity" for later use on a reasonable scale with today's
technologies.
This consists of growing some form of crop,
usually wood from quick-growing trees, for gasification or chipping and
burning in a thermal power station. This is unsuitable for Cyprus on any
reasonable scale because of a lack of suitable large areas for the crop
cultivation and the water requirements of such crops.
This method is ideal in places like Iceland but
requires volcanic rock strata at a constant temperature of about 200°C. The
island's volcanic origins in the Troodos massif have cooled down to much
lower temperatures than this, so it cannot be considered in this context.
Medium to large-scale poultry, cattle and pig
farming, such as is practised on the island, produces large amounts of
excrement. If this is placed in a large anaerobic digester, the gas produced
by fermentation in the first 48 hours can be collected and large quantities
of methane (or natural gas) can be easily separated. This gas is
indistinguishable from fossil natural gas and can be used for any similar
purpose. If transported to power stations, it could complement other fuels,
providing a small percentage of the island's power supply.
In a number of countries, up to ten percent of
electricity requirements are being supplied by enhancing the value of
household garbage and other combustible waste. This is .most practical in
regions of high population density, such as large cities. This would
certainly be practicable in Cyprus This would also reduce the need for
the many, unsightly, polluting, insanitary landfills, a few of which would
be used only to dispose the sterile cinders. Such power stations are not
cheap to construct, as the exhaust gases have to be scrubbed to eliminate
harmful pollutants, but they do make a useful contribution to the
environment.
There is, however, a big "but" to this idea and
it is one which will not fit in easily to the present Cypriot mentality: it
will require sorting of household waste (see
the essay on Waste recycling). In particular, glass and aluminium
are undesirable. Notwithstanding, this will become a requirement under EU
directives, anyway.
I am convinced that this technology
would make a useful contribution to Cyprus' environment and have
made a small study to examine the viability. This started with a
visit to an existing plant, in Switzerland, to learn about the
system. A description of my visit is the subject of an
essay on Tridel SA. After
this, I looked at the possibilities of the implementation of the
same technology in this country, the subject of the
essay on waste enhancement
in Cyprus. These proved very positive.
In the context of Cyprus, the only potentially
large scale variable renewable energy source is the solar photovoltaic
panel. A typical 3 kW installation costs about €20,000
and would produce electricity (not counting subsidies) to the tune of about
€300/year, based on the present cost of
fossil-fired electricity. It is clear that the price of the installation
would have to fall by 80% before it became economically viable. With the
subsidies, the payback period falls to between 8 and 10 years, which is just
acceptable. The Government should make the bureaucracy of obtaining such
subsidies easier. Notwithstanding, the full 20 percent of peak demand is a
long way off. The only major potential constant renewable energy source,
capable of supplying up to 10 per cent of our needs, would be by waste
incineration. I strongly urge that this be implemented, not just for
electricity supply but also as a logical means of introducing waste
discipline. A small contribution to any future natural-gas electricity
generation may be made by composting farm animal excrement, the residues
being a valuable natural fertiliser.
EU Directive 2001/77/EC
Οδηγία 2001/77/ΕΚ
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