But they only work when the wind is moving at a specific pace. How sustainable is wind turbine manufacture? Well, the International Renewable Energy Agency expects millions of tonnes of used turbine blades to be in reuse by This is due to the absence of commercially viable recycling solutions and can only be put in place when lifetime and quality allow.

But many of the current composite blades wind up in landfill. To combat this, turbine manufacturer, VESTAS , is researching composite recycling technologies with the aim of achieving zero-waste wind turbines by Hydropower plants run much the same as a coal-fired power plant does. By turning turbines with the force of water, hydropower facilities produce electricity.

For instance, the steam produced when coal is burnt in a coal plant powers turbines, which subsequently produce electricity. Water is used as the energy source in hydropower systems. But the most well-known type of hydropower, usually referred to as hydroelectric power, is a sizable dam that stores water in a reservoir.

Water is released from the reservoir when energy is required, and the water then drives turbines to generate electricity. In addition to being a cost-effective source of renewable electricity, hydropower is also one of the most economical energy sources overall.

Additionally, hydroelectricity is immune to the erratic price fluctuations of energy commodities since it harnesses the self-renewing force of rivers. Geothermal power uses heat from the earth to produce electricity.

It works well in areas with high temperatures because the temperature difference between the hot rocks underground and the surface creates an electric current. At present, geothermal energy is largely untapped. So, what are the challenges that we must overcome to take advantage of this practically limitless source of energy?

It also needs to be properly managed through the maintenance of underground reservoirs and has one of the highest upfront costs. But all this pales in comparison to the most controversial topic concerning geothermal energy.

Hydraulic fracturing, or fracking, is a method for extracting oil, natural gas, geothermal energy, or water from deep underground. Not least due to the risk of triggering earthquakes. One of the most active geothermal areas in the world is called the Ring of Fire, which encircles the Pacific Ocean.

The environment benefits directly the more we use renewable energy sources. Wind has powered boats to sail the seas and windmills to grind grain. The sun has provided warmth during the day and helped kindle fires to last into the evening.

But over the past years or so, humans increasingly turned to cheaper, dirtier energy sources, such as coal and fracked gas. Now that we have innovative and less-expensive ways to capture and retain wind and solar energy, renewables are becoming a more important power source, accounting for more than 12 percent of U.

energy generation. The expansion in renewables is also happening at scales large and small, from giant offshore wind farms to rooftop solar panels on homes, which can sell power back to the grid. Even entire rural communities in Alaska, Kansas, and Missouri are relying on renewable energy for heating and lighting.

Nonrenewable sources of energy are only available in limited amounts. Nonrenewable energy sources are also typically found in specific parts of the world, making them more plentiful in some nations than others. By contrast, every country has access to sunshine and wind. Many nonrenewable energy sources can endanger the environment or human health.

To top it off, all of these activities contribute to global warming. Humans have been harnessing solar energy for thousands of years—to grow crops, stay warm, and dry foods.

Solar, or photovoltaic PV , cells are made from silicon or other materials that transform sunlight directly into electricity.

Distributed solar systems generate electricity locally for homes and businesses, either through rooftop panels or community projects that power entire neighborhoods. Solar farms can generate enough power for thousands of homes, using mirrors to concentrate sunlight across acres of solar cells.

Solar supplies nearly 3 percent of U. electricity generation some sources estimate it will reach nearly 4 percent in But 46 percent of all new generating capacity came from solar in Today, turbines as tall as skyscrapers—with turbines nearly as wide in diameter—stand at attention around the world.

Wind, which accounts for 9. electricity generation , has become one of the cheapest energy sources in the country.

Top wind power states include California, Iowa, Kansas, Oklahoma, and Texas, though turbines can be placed anywhere with high wind speeds—such as hilltops and open plains—or even offshore in open water.

Hydropower is the largest renewable energy source for electricity in the United States, though wind energy is soon expected to take over the lead.

Nationally and internationally , large hydroelectric plants—or mega-dams —are often considered to be nonrenewable energy. Mega-dams divert and reduce natural flows, restricting access for animal and human populations that rely on those rivers.

Small hydroelectric plants an installed capacity below about 40 megawatts , carefully managed, do not tend to cause as much environmental damage, as they divert only a fraction of the flow. Biomass is organic material that comes from plants and animals, and includes crops, waste wood, and trees.

When biomass is burned, the chemical energy is released as heat and can generate electricity with a steam turbine. Biomass is often mistakenly described as a clean, renewable fuel and a greener alternative to coal and other fossil fuels for producing electricity. However, recent science shows that many forms of biomass—especially from forests—produce higher carbon emissions than fossil fuels.

There are also negative consequences for biodiversity. Moving to a clean energy grid is a must. So is being able to reliably supply affordable energy for everyone when they need it. Capital Power is committed to supplying reliable and affordable electricity to our communities — and achieving our fleet target of net zero by To learn more about our approach, innovations and commitment to reliability and decarbonization, please see:.

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These figures only measure potential exposure to toxic elements for workers. They do not give us estimates of potential death rates, which is why we do not include them in our referenced figures above.

However, the inclusion of these figures would not change the relative results, overall. Fossil fuels — coal, in particular — have a higher carcinogenic toxicity than both nuclear and renewables.

Hence the relative difference between them would actually increase, rather than decrease. The key insight would still be the same: fossil fuels are much worse for human health, and both nuclear and modern renewables are similarly safe alternatives.

However, estimates of the health burden of rare minerals in energy supply chains is still an important gap to fill, so that we can learn about their impact and ultimately reduce these risks moving forward. This article was first published in It was last updated in July based on more recent analysis and estimates.

Jones, Michael O'Sullivan, Robbie M. Andrew, Dorothee, C. Bakker, Judith Hauck, Corinne Le Quéré, Glen P. Peters, Wouter Peters, Julia Pongratz, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Rob B.

Jackson, Simone R. Alin, Peter Anthoni, Nicholas R. Bates, Meike Becker, Nicolas Bellouin, Laurent Bopp, Thi Tuyet Trang Chau, Frédéric Chevallier, Louise P.

Chini, Margot Cronin, Kim I. Currie, Bertrand Decharme, Laique M. Djeutchouang, Xinyu Dou, Wiley Evans, Richard A. Feely, Liang Feng, Thomas Gasser, Dennis Gilfillan, Thanos Gkritzalis, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Özgür Gürses, Ian Harris, Richard A.

Houghton, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Ingrid T. Luijkx, Atul Jain, Steve D. Jones, Etsushi Kato, Daniel Kennedy, Kees Klein Goldewijk, Jürgen Knauer, Jan Ivar Korsbakken, Arne Körtzinger, Peter Landschützer, Siv K.

Lauvset, Nathalie Lefèvre, Sebastian Lienert, Junjie Liu, Gregg Marland, Patrick C. McGuire, Joe R. Melton, David R. Munro, Julia E. S Nabel Shin-Ichiro Nakaoka, Yosuke Niwa, Tsuneo Ono, Denis Pierrot, Benjamin Poulter, Gregor Rehder, Laure Resplandy, Eddy Robertson, Christian Rödenbeck, Thais M Rosan, Jörg Schwinger, Clemens Schwingshackl, Roland Séférian, Adrienne J.

Sutton, Colm Sweeney, Toste Tanhua, Pieter P Tans, Hanqin Tian, Bronte Tilbrook, Francesco Tubiello, Guido van der Werf, Nicolas Vuichard, Chisato Wada Rik Wanninkhof, Andrew J. Watson, David Willis, Andrew J. Wiltshire, Wenping Yuan, Chao Yue, Xu Yue, Sönke Zaehle, Jiye Zeng.

Global Carbon Budget , Earth Syst. Data, Per capita electricity consumption in the EU in was around 6, kWh. The following sources were used to calculate these death rates. Electricity generation and health. The Lancet , , These figures are based on the most recent estimates from UNSCEAR and the Government of Japan.

In a related article , I detail where these figures come from. I have calculated death rates by dividing this figure by cumulative global electricity production from nuclear from to , which is 96, TWh.

However, this period excludes some very large hydropower accidents which occurred prior to I have therefore calculated a death rate for hydropower from to based on the list of hydropower accidents provided by Sovacool et al.

Since this database ends in , I have also included the Saddle Dam accident in Laos in , which killed 71 people. The total number of deaths from hydropower accidents from to was approximately , I have calculated death rates by dividing this figure by cumulative global electricity production from hydropower from to , which is , TWh.

Balancing safety with sustainability: assessing the risk of accidents for modern low-carbon energy systems. Journal of Cleaner Production , , In this analysis, the authors compiled a database of as many energy-related accidents as possible based on an extensive search of academic databases and news reports and derived death rates for each source from to UNSCEAR Sources and effects of Ionizing Radiation.

UNSCEAR Report to the General Assembly with Scientific Annexes. Available online. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation. General Assembly Official Records, Sixty-eighth session, Supplement No.

New York: United Nations, Sixtieth session, May 27—31, Schlömer S. Bruckner, L. Fulton, E. Hertwich, A. McKinnon, D. Perczyk, J. Roy, R.

Schaeffer, R. Sims, P. Smith, and R. Wiser, Annex III: Technology-specific cost and performance parameters. In: Climate Change Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O.

Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. A three-unit plant using quite different 1 MW CETO 6 units is being deployed by Carnegie with WaveHub in the UK — these generate power inside the buoyant actuator attached to a pump tethered to the seabed, replacing the closed hydraulic loop with an export cable.

The project capacity is now reported as 5 MWe. A large vertical panel harnesses up to 2 MW of wave energy and generates power in the fixed power take-off section anchored to the near-shore seabed 8 to 20 metres deep.

Numerous practical problems have frustrated progress with wave technology, not least storm damage. Ocean thermal energy conversion OTEC has long been an attractive idea, but is unproven beyond small pilot plants up to 50 kWe, though in a kWe closed cycle plant was commissioned in Hawaii and connected to the grid.

It works by utilising the temperature difference between equatorial surface waters and cool deep waters, the temperature difference needing to be about 20ºC top to bottom. In the open cycle OTEC the warm surface water is evaporated in a vacuum chamber to produce steam which drives a turbine.

It is then condensed in a heat exchanger by the cold water. The main engineering challenge is in the huge cold water pipe which needs to be about 10 m diameter and extend a kilometre deep to enable a large water flow. A closed cycle variation of this uses an ammonia cycle. The ammonia is vapourized by the warm surface waters and drives a turbine before being condensed in a heat exchanger by the cold water.

A 10ºC temperature difference is then sufficient. Beyond traditional direct uses for cooking and warmth, growing plant crops particularly wood to burn directly or to make biofuels such as ethanol and biodiesel has a lot of support in several parts of the world, though mostly focused on transport fuel.

More recently, wood pellets and chips as biomass for electricity generation have been newsworthy. The main issues here are land and water resources. The land usually must either be removed from agriculture for food or fibre, or it means encroaching upon forests or natural ecosystems.

Available fresh water for growing biofuel crops such as maize and sugarcane and for processing them may be another constraint.

Burning biomass for generating electricity has some appeal as a means of indirectly using solar energy for power. It is driven particularly by EU energy policy which classifies it as renewable and ignores the CO 2 emissions from burning the wood product. However, the logistics and overall energy balance may defeat it, in that a lot of energy — mostly oil based — is required to harvest and move the crops to the power station.

This means that the energy inputs to growing, fertilising and harvesting the crops then processing them can easily be greater than the energy value in the final fuel, and the greenhouse gas emissions can be greater than those from equivalent fossil fuels.

Also other environmental impacts related to land use and ecological sustainability can be considerable. For long-term sustainability, the ash containing mineral nutrients needs to be returned to the land.

Some of this comes from low-value forest residues, but increasingly it is direct harvesting of whole trees. Drax demand is now about 7. No carbon dioxide emissions are attributed to the actual burning, on the basis that growing replacement wood balances out those emissions, albeit in a multi-decade time frame.

Unlike coal, the wood needs to be stored under cover. In Drax received £ million in subsidies for using biomass — mostly US wood pellets — as fuel, followed by £ million in A pilot bioenergy carbon capture storage BECCS project — the first in Europe — commenced at Drax in In central Europe, wood pellets are burned on a large scale, and it is estimated that about half the wood cut in the EU is burned for electricity or heating.

Worldwide, wood pellet burning is increasing strongly due both to subsidies and national policies related to climate change since carbon dioxide emissions from it are excluded from national totals. World statistics available on the Global Timber website.

In Australia and Latin America sugar cane pulp is burned as a valuable energy source, but this bagasse is a by-product of the sugar and does not have to be transported.

In solid biofuels provided TWh from 83 GWe installed capacity, biogas provided 88 TWh from 18 GWe and municipal waste provided 62 TWh from 13 GWe capacity IRENA figures.

In biomass and waste provided TWh of electricity worldwide, from GWe of capacity according to the IEA. However, such projections are increasingly challenged as the cost of biofuels in water use and role of biofuels in pushing up food prices is increasingly questioned.

In particular, the use of ethanol from corn and biodiesel from soybeans reduces food production and arguably increases world poverty. Over about 4 million hectares 40, km 2 of forest in Southeast Asia and South America are reported by Thomson Reuters to have been cleared for EU biofuel production: 1.

Most goes into biodiesel. A legislated portion of the US corn crop is turned into fuel ethanol, aided by heavy subsidies. In about million tonnes of US corn was used to make 58 GL of fuel ethanol most of the rest is stock food and production has declined since.

Meanwhile basic food prices rose, leading the Food and Agriculture Organization of the United Nations in mid to call for the USA to halt its biofuel production to prevent a food crisis. In any case, the energy return on investment EROI of corn ethanol in the USA is strongly questioned, and a consensus that it is below the minimum useful threshold is reported.

Ethanol is no longer promoted as good for the environment. Generally, burning biomass for electricity has been put forward as carbon neutral. That too is now questioned on the basis that carbon is released much more quickly than it can be absorbed by growing wood crops, so using round wood for pellets is likely to contribute significant net CO 2 emissions for many decades.

Using sawmill or logging residues however is not contentious. Some EU states have developed biomass sustainability criteria. A new technology, Pavegen , uses pavement tiles about one metre square to harvest energy from pedestrian traffic.

A footfall on a tile will flex it about 5mm and result in up to 8 watts of power over the duration of the footstep. Electricity can be stored, used directly for lighting, or in other ways. In the context of sustainable development it shares many of the benefits of many renewables, it is a low-carbon energy source, it has a very small environmental impact, similarities that are in sharp contrast to fossil fuels.

Nuclear fission power reactors do use a mineral fuel, and demonstrably but minimally deplete the available resources of that fuel. In the future nuclear power will make use of fast neutron reactors. As well as utilizing about 60 times the amount of energy from uranium, they will unlock the potential of using even more abundant thorium as a fuel.

In addition, some 1. The consequence of this is that the available resource of fuel for fast neutron reactors is so plentiful that under no practical terms would the fuel source be significantly depleted.

Most also tend to make very large demands on resources to construct the plant used for harnessing the natural energy — per kilowatt hour produced, much more than nuclear power. Wind turbine plants need over ten times the amount of steel, 15 times the amount of copper and more than twice the amount of other critical minerals than nuclear power per kWh output.

Inertia is a key element of electricity grid stability. To compensate for the lack of synchronous inertia in generating plant when there is high dependence on wind and solar sources, synchronous condensers, sometimes known as rotating stabilisers, may be added to the system.

These are high-inertia rotating machines that can support the grid network in delivering efficient and reliable synchronous inertia and can help stabilize frequency deviations by generating and absorbing reactive power.

They behave like a synchronous motor with no load, providing reactive power and short-circuit power to the transmission network. Synchronous condensers syncons are like synchronous motors with no load and not mechanically connected to anything.

They may be supplemented by a flywheel to increase inertia. They are used for frequency and voltage control in weak parts of a grid or where there is a high proportion of variable renewable input requiring grid stability to be enhanced.

Adding synchronous condensers can help with reactive power needs, increase short-circuit strength and thus system inertia, and assure better dynamic voltage recovery after severe system faults.

They can compensate for either a leading or lagging power factor, by absorbing or supplying reactive power measured in volt-ampere reactive, VAr to the line.

Static synchronous compensators STATCOM have a voltage control function, but not the full syncon function. A leading application is in Germany, where a highly variable flow from offshore wind farms in the north is transmitted to the main load centres in the south, leading to voltage fluctuations and the need for enhanced reactive power control.

The reduced inertia in the entire grid made the need to improve short-circuit strength and frequency stability more critical. Amprion has ordered two MVAr static synchronous compensators STATCOM from Siemens for Polsum in North Rhine-Westphalia and Rheinau in Baden-Württemberg to help stabilize the power grid as conventional plant closures increase the loss of inertia risk with increasing volatility from renewables.

Also a large GE synchronous condenser is installed at Bergrheinfeld in Bavaria. Following a state-wide blackout, South Australia is installing two GE synchronous condensers at Davenport near Port Augusta and two Siemens units at Robertstown to compensate for a high proportion of wind input to the grid and reduce the vulnerability to further problems from this.

These are connected to the kV grid. Also a MVAr Siemens machine is installed at the MWe Kiamal solar PV farm just across the Victorian border near Ouyen. GE has converted a MWe generator retired from a coal-fired plant to a synchronous condenser of over MVAr, and such conversions, powered from the grid, are often cost-effective.

After the MWe Biblis A nuclear power plant in Germany was retired in its generator was converted to a synchronous condenser. In the UK, Statkraft plans to install two GE rotating stabilisers to provide stability services to the transmission network in Scotland.

These would draw about 1 MWe from the grid and enable many times that of intermittent renewable input, replacing the role of inertia in fossil-fuel or nuclear plants for frequency control. The project is among five innovative grid stability contracts awarded by the National Grid electricity system operator in January GE quotes rotor mass of tonnes for its horizontal axis 65 MVAr machine and t for a MVAr vertical axis machine compared with over t for a large conventional power plant.

In the small Denmark grid, five machines are required to dampen the effect of about 5 GWe of wind capacity. It has a MVAr Siemens syncon at Bjaerskov. Siemens quotes horizontal axis units up to MVAr, ABB up to MVAr, and GE to MVAr.

Some newer wind turbines are directly coupled and run synchronously at fixed grid-defined rotation speeds, providing some frequency stability, although less total energy output than with DC output. Centralised state utilities focused on economies of scale can easily overlook an alternative model — of decentralized electricity generation, with that generation being on a smaller scale and close to demand.

Here higher costs may be offset by reduced transmission losses not to mention saving the capital costs of transmission lines and possibly increased reliability. Generation may be on site or via local mini grids.

In some places pumped hydro storage is used to even out the daily generating load by pumping water to a high storage dam during off-peak hours and weekends, using the excess base-load capacity from low-cost coal or nuclear sources.

During peak hours this water can be used for hydro-electric generation. It is not well suited to filling in for intermittent, unscheduled generation such as wind, where surplus power is irregular and unpredictable.

In , GWh was supplied from pumped storage according to IRENA. There is increasing interest in off-river pumped hydro ORPH storage, with pairs of reservoirs having at least metres height difference.

Building power storage emerged in as a defining energy technology trend. See companion information paper on Electricity and Energy Storage. It is clear that renewable energy sources have considerable potential to meet mainstream electricity needs.

However, having solved the problems of harnessing them there is a further challenge: of integrating them into the supply system where most demand is for continuous, reliable supply.

Obviously sun, wind, tides and waves cannot be controlled to provide directly either continuous dispatchable power to meet base-load demand, or peak-load power when it is needed, so how can other, dispatchable sources be operated so as to complement them?

If there were some way that large amounts of electricity from intermittent variable renewable energy VRE producers such as solar and wind could be stored efficiently, the contribution of these technologies to supplying electricity demand would be much greater — see preceding subsection.

The only renewable source with built-in storage and hence dispatchable on demand is hydro from dams. The storage can be enhanced by pumping back water when power costs are low, and such dammed hydro schemes can be complemented by off-river pumped hydro.

This requires pairs of small reservoirs in hilly terrain and joined by a pipe with pump and turbine. There is some scope for reversing the whole way we look at power supply, in its hour, 7-day cycle, using peak load equipment simply to meet the daily peaks.

Conventional peak-load equipment can be used to some extent to provide infill capacity in a system relying heavily on VRE sources such as wind and solar. Its characteristic is rapid start-up, usually apart from dammed hydro with low capital and high fuel cost.

Such capacity complements large-scale solar thermal and wind generation, providing power at short notice when they were unable to. This is essentially what happens with Denmark, whose wind capacity is complemented by a major link to Norwegian hydro as well as Sweden and the north German grid.

West Denmark the main peninsula part is the most intensely wind-turbined part of the planet, with 1. In , 3.

On two occasions, in March and April, wind supplied more than total demand for a few hours. In February during a cold calm week there was virtually no wind output. However, all this can be and is managed due to the major interconnections with Norway, Sweden and Germany, of some MWe, MWe and MWe respectively.

Furthermore, especially in Norway, hydro resources can normally be called upon, which are ideal for meeting demand at short notice. though not in after several dry years.

So the Danish example is a very good one, but the circumstances are far from typical. The report from a thorough study commissioned by the German Energy Agency DENA looked at regulating and reserve generation capacity and how it might be deployed as German wind generation doubled to The study found that only a very small proportion of the installed wind capacity could contribute to reliable supply.

This all involves a major additional cost to consumers. The performance of every UK wind farm can be seen on the Renewable Energy Foundation website. Note particularly the percentage of installed capacity which is actually delivering power averaged over each month.

If hydro is the back-up and is not abundant, it will be less available for peaking loads. If gas is the back-up this will usually be the best compromise between cost and availability.

But any conventional generating plants used as back-up for VRE sources has to be run at lower output than designed to accommodate the intermittent input, and then the lower capacity factor can make them uneconomic, as is now being experienced with many GWe of gas and coal capacity in Germany.

The higher the proportion of intermittent input to a system, the greater the diseconomy. This incidentally has adverse CO 2 emissions implications.

See sections below. This value decline caused by wind and solar generating most of their output during times of self-imposed electricity oversupply is marked and it magnifies with their share increasing. This price effect is not compensated by the price peaks enjoyed by reliable producers when those renewables are insufficient.

The price volatility is a major disincentive to investment in new plant, whether nuclear or renewable, if not regulated or subsidized. Since wind and solar PV output correlates with meteorological conditions across a wide area, an increased proportion of them also means that the average price received by those producers — especially solar PV — declines significantly as their penetration increases, magnifying this value decline.

At a penetration level of Nevertheless, VRE sources make an important contribution to the world's energy future, even if they cannot carry the main burden of supply. The Global Wind Energy Council expects wind to be able to supply between In the OECD International Energy Agency IEA published a report on this issue : The Power of Transformation , wind, sun and the economics of flexible power systems.

It said that the cost-effective integration of variable renewable energy VRE has become a pressing challenge for the energy sector. Meanwhile Germany provides a case study in accelerated integration of VRE into a stable system, with both politically- and economically-forced retirement of conventional generating capacity.

See also the information paper on Energiewende. Thus the PTC meant that intermittent wind generators could dump power on the market to the extent of depressing the wholesale price so that other generators were operating at a loss. This market distortion has created major problems for the viability of dispatchable generation sources upon which the market depends.

Grid management authorities faced with the need to be able to dispatch power at short notice treat wind-generated power not as an available source of supply which can be called upon when needed but as an unpredictable drop in demand.

Thus, building 25 GWe of wind capacity, equivalent to almost half of UK peak demand, will only reduce the need for conventional fossil and nuclear plant capacity by 6. Also, some 30 GWe of spare capacity will need to be on immediate call continuously to provide a normal margin of reserve and to back up the wind plant's inability to produce power on demand — about two-thirds of it being for the latter.

Ensuring both secure continuity of supply reliably meeting peak power demands and its quality voltage and frequency control means that the actual potential for wind and solar input to a system is limited. Doing so economically, as evident from the above UK figures, requires low-cost back-up such as hydro, or gas turbine with cheap fuel.

Nuclear power plants are essentially base-load generators, running continuously. Where it is necessary to vary the output according to daily and weekly load cycles, for instance in France, where there is a very high reliance on nuclear power, they can be adapted to load-follow.

For BWRs this is reasonably easy without burning the core unevenly, but for a PWR as in France to run at less than full power for much of the time depends on where it is in the 18 to month refueling cycle, and whether it is designed with special control rods which diminish power levels throughout the core without shutting it down.

So while the ability on any individual PWR reactor to run on a sustained basis at low power decreases markedly as it progresses through the refueling cycle, there is considerable scope for running a fleet of reactors in load-following mode.

Generation III plants and small modular reactors have more scope for load-following, and as fast neutron reactors become more established, their ability in this regard will be an asset. If electricity cannot be stored on a large scale, the next logical step is to look at products of its use which can be stored, and hence where intermittent electricity supply is not a problem.

In contrast to renewable hydro, the feed-in of wind and solar output is uncontrollably intermittent due to the uncertainty of meteorological conditions. In grid management terms they are not dispatchable.

Therefore the energy system needs backup capacity from the on-demand-sources to bridge periods with high or low generation from renewables. To some extent battery storage can help, though most grid-scale battery installations are more for ancillary services frequency control etc.

rather than energy storage. See also Electricity and Energy Storage information page. But that is not the main problem. Wind and solar power supply is largely governed by wind speed and the level of sunlight, which can only loosely be related to periods of power demand.

It is this feature of intermittent renewable power supply that results in the imposition of additional costs on the generating system as a whole.

The third category of intermittent renewable integration cost is grid interconnection. Wind and solar farms are ideally sited in areas that experience high average wind speeds and high average solar radiation respectively.

These sites are often, even typically, distant from areas of electricity demand. Transmission and distribution networks will often need to be extended significantly to connect sources of supply and demand - this is a current challenge in UK and North Germany.

The impact of high levels of intermittent, low cost power will be to reduce the load factors of base-load power generators, and thereby increase their unit costs per kilowatt-hour. Given the high capital costs of nuclear, such an impact will significantly increase the levelised generation costs of nuclear.

Hydrogen is widely seen as a possible fuel for transport, if certain problems can be overcome economically. It may be used in conventional internal combustion engines, or in fuel cells which convert chemical energy directly to electricity without normal burning.

Making hydrogen requires either reforming natural gas methane with steam, or the electrolysis of water. The former process has carbon dioxide as a by-product, which exacerbates or at least does not improve greenhouse gas emissions relative to present technology.

With electrolysis, the greenhouse burden depends on the source of the power. But if these sources are used for electricity to make hydrogen, then they can be utilised fully whenever they are available, opportunistically.

Broadly speaking it does not matter when they cut in or out, the hydrogen is simply stored and used as required. However, electrolysers are inefficient at low capacity factors such as even dedicated wind or solar input would supply.

A quite different rationale applies to using nuclear energy or any other emission-free base-load plant for hydrogen. Here the plant would be run continuously at full capacity, with perhaps all the output being supplied to the grid in peak periods and any not needed to meet civil demand being used to make hydrogen at other times.

About 55 kWh is required to produce a kilogram of hydrogen by electrolysis at ambient temperature, so the cost of the electricity clearly is crucial. Renewable energy sources have a completely different set of environmental costs and benefits to fossil fuel or nuclear generating capacity.

On the positive side they emit no carbon dioxide or other air pollutants beyond some decay products from new hydro-electric reservoirs , but because they are harnessing relatively low-intensity energy, their 'footprint' — the area taken up by them — is necessarily much larger.

Whether Australia could accept the environmental impact of another Snowy Mountains hydro scheme providing some 3. Whether large areas near cities dedicated to solar collectors will be acceptable, if such proposals are ever made, remains to be seen.

Beyond utilising roofs, MWe of solar capacity would require at least 20 square kilometres of collectors, shading a lot of country. In Europe, wind turbines have not endeared themselves to neighbours on aesthetic, noise or nature conservation grounds, and this has arrested their deployment in UK.

At the same time, European non-fossil fuel obligations have led the establishment of major offshore wind forms and the prospect of more. However, much environmental impact can be reduced.

Fixed solar collectors can double as noise barriers along highways, roof-tops are available already, and there are places where wind turbines would not obtrude unduly.

In an open market, government policies to support particular generation options such as renewables normally give rise to explicit direct subsidies along with other instruments such as feed-in tariffs, quota obligations and energy tax exemptions.

In the EU, feed-in tariffs are widespread. Corresponding to these in the other direction are taxes on particular energy sources, justified by climate change or related policies. For instance Sweden taxes nuclear power at about EUR 0.

European Environment Agency figures in gave indicative estimates of total energy subsidies in the EU for solid fuel coal EUR Thus, various schemes are operating in Europe, mainly feed-in tariffs, fixed premiums, green certificate systems and tendering procedures.

These schemes are generally complemented by tax incentives, environmental taxes, contribution programs or voluntary agreements. France had a feed-in tariff of EUR 8. Germany's Renewable Energy Sources Act gives renewables priority for grid access and power dispatch.

It is regularly amended to adapt feed-in tariffs to market conditions and technological developments. For wind energy an initial tariff applies for up to 20 years and this then reduces to a basic tariff of EUR 5.

The initial tariff is EUR 9. Denmark has a wide range of incentives for renewables and particularly wind energy. It has a complex 'Green Certificate' scheme which transfers the subsidy cost to consumers. However, there is a further economic cost borne by power utilities and customers.

When there is a drop in wind, back-up power is bought from the Nordic power pool at the going rate. Similarly, any surplus subsidised wind power is sold to the pool at the prevailing price, which is sometimes zero. The net effect of this is growing losses as wind capacity expands.

Spain has different levels of feed-in tariffs depending on the technology used. A fixed tariff of EUR 7. The tariffs for renewables are adjusted every four years.

Greece has a feed-in tariff of 6. The UK has not used any feed-in tariff arrangement, but is to do so from Meanwhile a specific indication of the cost increment over power generation from other sources is given by the 4.

In addition there is a Climate Change Levy of 0. Sweden subsidises renewables principally large-scale hydro by a tax on nuclear capacity, which works out at about EUR 0.

Based on the capacity factors above, you would need almost two coal or three to four renewable plants each of 1 GW size to generate the same amount of electricity onto the grid.

Suggested Read: What is Generation Capacity? Office of Nuclear Energy Nuclear Power is the Most Reliable Energy Source and It's Not Even Close. Just how reliable has nuclear energy been?

To better understand what makes nuclear so reliable, take a look at the graph below.