Battle of the grids

Nuclear Monitor Issue: 
Jan Van De Putte and Rebecca Short, Greenpeace International

In 'Battle of the Grids' a report released on January 18 by Greenpeace, researchers claim that solar energy in Europe's south and wind energy from the north could supply 68 percent of the 27-nation EU's electricity needs in 2030 and 99.5 percent by the middle of the century. However, that would require governments to change policy tack and favor investments in green energy to the tune of 70 billion euros (94 billion US$) by 2030 and another 28 billion euros over the following decade. "It's a question of choice."

Europe’s electricity grid is characterised by big, polluting power stations pumping out constant energy, regardless of consumer need. Climate policy and consumer demand are hurtling us towards a smarter, more efficient Europe-wide grid opening up vast new technological, business and consumer opportunities. Taken with Greenpeace's 2010 Energy [R]evolution report, Battle of the Grids builds on Greenpeace's earlier Renewables 24/7 study. It is a manual for the kind of system we need to deliver 68 percent renewable energy by 2030 and nearly 100 percent by 2050

Battle of the Grids: what’s the big barrier?
Power from some renewable plants, such as wind and solar, varies during the day and week. Some see this as an insurmountable problem, because up until now we have relied on coal or nuclear to provide a fixed amount of power at all times.  The title of this report refers to the struggle to determine which type of infrastructure or management we choose and which energy mix to favour as we move away from a polluting, carbon intensive energy system.

Some important facts include:
• electricity demand fluctuates in a predictable way.
• smart management can work with big electricity users, so their peak demand moves to a different part of the day, evening out the load on the overall system.
• electricity from renewable sources can be stored and ‘dispatched’ to where it is needed in a number of ways, using advanced grid technologies.

Wind-rich countries in Europe are already experiencing conflict between renewable and conventional power. In Spain, where a lot of wind and solar is now connected to the grid, gas power is stepping in to bridge the gap between demand and supply. This is because gas plants can be switched off or run at reduced power, for example when there is low electricity demand or high wind production. As we move to a mostly renewable electricity sector, gas plants will be needed as backup for times of high demand and low renewable production.

Effectively, a kWh from a wind turbine effectively displaces a kWh from a gas plant, avoiding carbon dioxide emissions. Renewable electricity sources such as thermal solar plants (CSP), geothermal, hydro, biomass and biogas can gradually phase out the need for natural gas. The gas plants and pipelines would then progressively be converted for transporting biogas.

Baseload blocks progress
Generally, coal and nuclear plants run as so-called baseload, meaning they work most of the time at maximum capacity regardless of how much electricity consumers need. When demand is low the power is wasted. When demand is high additional gas is needed as a backup. Coal and nuclear cannot be turned down on windy days. Instead, wind turbines will get switched off to prevent overloading the system. The fall in electricity demand that accompanied the recent global economic crisis revealed system conflict between inflexible baseload power, especially nuclear, and variable renewable sources, especially wind power, with wind operators told to  shut off their generators. In Northern Spain and Germany, this uncomfortable mix is already exposing the limits of the grid capacity. If Europe continues to support nuclear and coal power alongside a growth in renewables, clashes will occur more and more, creating a bloated, inefficient grid.

Despite the disadvantages stacked against renewables, they have begun to challenge the profitability of older plants. After construction costs, a wind turbine is generating electricity almost for free and without burning any fuel. Meanwhile, coal and nuclear plants use expensive and highly polluting fuels. Even where nuclear plants are kept running and wind turbines are switched off, conventional energy providers are concerned. like any commodity, oversupply reduces price across the market. In energy markets, this affects nuclear and coal too. We can expect more intense conflicts over access to the grids over the coming years. One example is the tension in Germany over whether to extend the lifetime of nuclear reactors by 8-14 years. The German renewable energy federation (BEE) has warned its government that this would seriously damage the further expansion of renewable energy. It predicts that renewable energy could provide half of Germany’s supply by 2020, but this would only make economic sense if half the nuclear and coal plants were phase-out by that date.

This explains why conventional utilities are growing increasingly critical of a continued and stable growth of renewables beyond 2020.

Planned phase out of nuclear and coal
If we want to reap the benefits of a continued and speedy growth of renewable energy technologies, they need priority access to the grid and we urgently have to phase out inflexible nuclear.

The Energy [R]evolution is a detailed market analysis which shows that we can reach 68 percent renewable electricity by 2030 and almost 100 percent by 2050. It also lays out a future scenario where electricity demand keeps growing, even with large-scale efficiency, because of electric vehicles displacing cars. This 2030 renewables target requires:
• an almost entire (90 percent) phaseout of coal and nuclear power by 2030.
• continued use of gas plants, which emit about half the CO2 per kWh compared to a coal plant.

The result: CO2 emissions in the electricity sector can fall by 65 percent in 2030 compared to 2007 levels. Between 2030 and 2050 gas can be phased out and we reach an almost 100 percent renewable and CO2-free electricity supply.

Six steps to build the grid for renewable Europe 24/7

1- More lines to deliver renewable electricity where it is needed:
The first step in our methodology to develop a 100 percent renewable electricity system is to add more electricity lines to the base-line of the existing high-voltage grid of 2010. lines will be needed especially from areas with overproduction, e.g. south of Europe in the summer, to areas with a high demand like Germany. This allows a  more efficient use of the installed solar power. In winter months, the opposite could happen, when a large oversupply of wind power is transported from the north of Europe south to population centres. It is common for both wind speeds and solar radiation to vary across Europe concurrently, so interconnecting the variable  renewables in effect ‘smoothes out’ the variations at any one location. Adding more grid infrastructure increases security of supply and makes better use of renewable energy sources. It also means backup capacity in Europe can be used more economically because biomass, hydro or gas plants in one region can be transferred to another region. In this first step, lines are added to a point that is called the Base Model, electricity supply is secured in the whole of Europe 24 hours a day, seven days a week.

Long distance transport to stop energy loss

The Base Model focuses only on securing the supply of electricity around the clock. Our model revealed the unexpected problem that very large amounts of variable renewable sources cannot always be delivered because of bottlenecks in the grid. This problem occurs when periods of high wind or sun combine with low demand locally. Because this oversupply cannot be used in the same region, wind turbines or solar plants have to be shut down. In the Base Model, renewable losses total 346TWh per year, or 12 percent of what these energy sources could have produced without any constraints in the grid. This represents economic losses of 34.6bn€/year.

However, renewable losses can be reduced by transporting electricity over longer distances in Europe from areas of oversupply to those with a net demand for electricity. The illustration below shows a large oversupply of renewable sources at an Italian node, while there is an undersupply in the UK over the same period. Electricity transmission from the Italian node to the UK will smooth the differences and make better economic use of the installed renewable sources.

2- Priority for renewable energy on the European grid to reduce losses
The Base Model assumes a clear priority access for renewable energy at each of the nodes. This reflects the situation in many European countries which give some level of priority at the national level. However, there are no clear priority rules at the European level, including on the interconnections between countries. For example, wind turbines in Germany currently do not have a priority over nuclear power plants in France in providing energy to the European grid. This study also examines the effect of changing the rules to give priority to renewable sources throughout Europe, including on all interconnections, which does not require any additional investment. Under this scenario, the use of renewable sources would increase dramatically and constraining losses would be massively reduced. Just by improving regulation this way, without putting security of supply at risk, renewable losses can be reduced from 12 to 4 percent, which would mean an annual saving of 248TWh of

electricity or 24.8bn€/year.

Under such a new dispatch method, energy production from solar PV and wind would increase by 10 percent and 32 percent in 2030 over the base scenario without priority dispatch. And with increased generation from clean sources, generation from fossil-fuel sources will drop even more. This is particularly noticeable for power generated by gas, which would be 5 percent lower than in the Base Scenario. For a 100 percent renewable 2050, priority rules are needed between renewable sources. Variable renewables such as wind and solar PV will get priority over dispatchable renewables such as stored hydro or biomass, which will serve as back-up.

3- Additional lines to allow renewable energy through the bottlenecks
Even with a clear priority dispatch of renewable sources at the European level, there is still a significant level of renewable losses, especially for offshore wind which loses 17 percent of what could be produced without any bottlenecks in the grid. For all renewable sources this loss represents 98TWh, 4 percent of total, and an economic loss of almost 10bn€ per year. To channel these oversupplies out of their regions would require further grid extension, in particular strengthening lines between the north and the south of Europe. There is also a need for more lines between large cities, such as London, and the offshore wind grid. To deal with this effect, Energynautics studied what level grids should be upgraded to in order to limit the losses of renewable electricity production due to bottlenecks. By 2030, an upgrade of 28bn€, assuming the most expensive option) would reduce the losses from 4 to 1 percent, or a net saving of 66TWh per year or 6.5bn€ per year. This level of additional investment in the grid would be recovered in just a few years. Offshore wind losses would be most significantly reduced, from 17 percent to only 4 percent. A similar approach is followed for 2050. Total investment required would be around 98bn€ up to 2030 and an additional 74bn€ or 581bn€ up to 2050 under the low and High Grid scenarios. This allow for the more expensive approach of underground lines and new technologies such as high-voltage direct current. Infrastructure like this has a 40 year lifetime, so for 2030 this investment equates to less than 1 percent of the total electricity cost.

4- Demand management and smart grids to reduce transmission losses (2030 only)
Demand management and storage (step 5) have a very similar impact on the electricity system. Demand-management shifts some demand from periods with a low supply of variable renewables to periods with a higher supply, while storage can store electricity from oversupply of variable renewables to be used during periods with an undersupply. Also referred to as demand-side management (DSM), this approach makes use of the range of technology in a smart grid. Demand management is already common practice in many areas of industry, but could be further extended to households through grids management technologies. For example, it is possible to communicate with refrigerators so they don’t run compressors during the typical peak demand of 6pm. Across whole districts this can make a difference to the demand or load curve. Demand-side management also helps to limit the losses in transporting electricity over long distances (which escapes as heat). Demand management simulations in this study are only done for 2030. For 2050, storage simulations are used to study different levels of demand management. Given the similarities between simulations for demand-management and storage, this simplification is legitimate.

5- Adding storage in the system (2030 and 2050)
Another essential way to even supply and demand is to add storage capacity, for example through pumped hydro plants, batteries from electric vehicles or molten salt storage for concentrating solar power. While storage is relatively expensive, this study optimised the cost balance between investing in storage and extending the grids. There needs be a balance between extending the grid and adding more storage. This study used cost optimisation to determine that point. As mentioned under step four, storage simulations are also used to study the impact of demand-management in 2050. Storage is factored at the European level, thus oversupply at one node can be stored at another, and this stored electricity can then be used as backup at any node in the European grid, a long as transport capacity is available. Storage and demand-management combined have a rather limited impact on the 2030 high-voltage grid. We can assume some impact at the distribution level (the more local grid), but this is not studied in this report. This relatively low impact by 2030 is a consequence of the 98bn€ investment in grids, as modelled in this report, which allows the smooth integration of up to 68 percent renewables, as long as 90 percent of ‘baseload’ coal and nuclear are phased out. However for 2050, integration of close to 100 percent renewable power is far more challenging for the electricity system than 68 percent in 2030, and storage and demand-management play a substantial role in balancing supply and demand. Especially in the low Grid scenario, which emphases a high regional production close to demand centres, storage and demand-management can decrease the curtailment of renewable electricity from 13 percent to 6 percent. We assume that by 2050, it will be possible to use a significant part of this curtailed electricity either for storage or other electricity use.

6- Security of supply: electricity 24/7 even if the wind doesn’t blow
Adding lines, storage and demand management all increase security of supply because even under an extreme weather event of low wind combined with low solar during winter, excess wind power from another region can be imported. To test the modelled system, the most extreme weather events over the last 30 years were identified and applied to the calculation. This is typically a winter period with low wind, when solar radiation is also low and demand is typically high. The model can then tell if the optimal system can withstand the test or if more electricity lines would have to be added. For the 2030 and 2050 models, the simulations prove that the optimised model is robust enough to withstand even the most extreme climatic events.

Spanish case study
The Spanish renewable electricity sector has grown impressively in recent years. Wind power capacity more than doubled in four years from 8.7GW in 2005 to 18.7GW by the end of 2009. Wind produced 16% in 2010, and all renewables together produced more electricity (35%) than nuclear power (21%) and coal (8%) together. It is projected that if renewable sources continue this growth rate, they would supply 50 percent by 2020.

However, while the market still showed a very dynamic growth over 2005 and 2006 with around 3GW of wind power installed each year, growth since has slowed down. For 2010, it is expected to remain at around 1GW. A combination of government caps on new installations and high uncertainty of regulation is to blame.

The actions of the Spanish government to slow the growth of renewables came after criticism from the large utilities. These companies have experienced a drop in profits of their coal and gas plants through a combination of a decreasing electricity demand due to the economic crisis, growth of new renewable supply and an inflexible nuclear baseload production. While gas plants capacity increased by 6 percent in 2009, their annual output was reduced by 14 percent, thereby lowering their average load factor to 38 percent.

The inflexibility of nuclear power output is clearly illustrated by the Nov. 9th 2010 event with a record-high wind production reaching almost 15GW of power and covering almost half of all Spanish electricity demand. As can be seen in the graph representing the electricity production of that day, the strong increase of renewable energy production was confronted with an inflexible (unchanged) nuclear baseload production which forced gas plants to constrain almost all of their energy output. Repeating similar events over the last two years, wind turbines had to be stopped, not because of grid limitations to transport wind power to demand centres, but because of oversupply caused by the ‘must run’ status of Spain’s nuclear plants. It is estimated that for 2010, some 200GWh of wind electricity will be curtailed by giving priority to nuclear power.

This problem caused by the inflexibility of nuclear plants will inevitably increase over the next years with the further growth of wind and solar power. As demonstrated in our simulations for 2030 in the report, a swift phase out of baseload power is needed to avoid economic losses in the electricity system. If this does not happen, it is the free, clean renewable electricity which has to be constrained.

The report Batle of the grids, is written by Jan Van De Putte and Rebecca Short. It is available at: