A new report by the Institute for Energy Economics and Financial Analysis (IEEFA) shows that major power systems are able to cope quite well with increasing shares of intermittent renewables, if the right measures are taken. The study says that increased generation of these renewables does not make the grid less reliable or compromise security of supply.
Critics of renewable energy have often warned that there are strict limits to the amount of intermittent power that the grid can handle. The U.S. government last year even commissioned a study to find out whether the stability of the grid is being threatened by the increase in renewables. (The conclusion was that it did not.)
Yet so far, despite strong growth of solar and wind, no limits appear to be on the horizon. The expansion of renewables does present challenges and require measures, but with the right measures, systems are able to cope quite well. So says a new report, “Power-Industry Transition, Here and Now,” from the Institute for Energy Economics and Financial Analysis (IEEFA), a U.S.-based private institute whose mission it is “to accelerate the transition to a diverse, sustainable and profitable energy economy.”
The IEEFA researchers looked at nine countries and regions which last year had shares of renewables ranging from 14.3% to 52.8%, while the global average was 5.2%:
- Denmark (52.8%)
- South Australia (48.4%)
- Uruguay (32.2%)
- Germany (26%)
- Ireland (24.6%)
- Spain (23.2%)
- Texas (18%)
- California (15%)
- the state of Tamil Nadu, India (14.3%)
The level of liberalization in these markets varies: they include liberalized, energy-only markets, markets with some state intervention, and markets with full state regulation.
To measure the reliability of the grid, the researchers looked at power outages as one indicator. They found no obvious link between wind and solar market share and longer outages. They did find a correlation between income per capita and duration of outages.
Investment in high-voltage transmission systems turns out to be one of the most critical steps to prepare for higher levels of variable renewables.
However, higher-income nations with average power outages of more than one hour, such as Sweden, the United States, Australia or Norway, have a lower market share of variable renewables, they note.
The study outlines various methods for countries to integrate a higher share of wind and solar power into their systems. There is no general rule as to which of the options to follow; countries should adopt and adjust these measures according to their specific needs. The report did not look into the cost of these measures.
Investment in high-voltage transmission systems turns out to be one of the most critical steps to prepare for higher levels of variable renewables, according to the researchers. Building transmission systems helps avoid curtailment, which can increase the cost of renewables generation.
Improving interconnections and cooperation with neighboring countries can help to balance and integrate larger shares of variable renewables.
For example, Texas managed to drastically reduce curtailment by expanding its transmission network. To connect the western part of the state, where most of the wind power is generated, with load centers in the eastern part, the state built 3,600 miles of new transmission lines between 2005 and 2014 at a cost of $6.8 billion. Although curtailment decreased significantly, the state still needs to build more connections as wind power capacities continue to rise.
Improving interconnections and cooperation with neighboring countries can also help to balance and integrate larger shares of variable renewables, the report says. For example, despite having the highest wind power market share in the world, Denmark has the lowest wind power curtailment among the studied markets. This, in large part, is the result of its strong interconnection with countries such as Sweden, Norway and Germany.
The country’s interconnection capacity today accounts for more than half of domestic generation (51%), which may rise to 59% by 2020. As a result, Denmark can import or export power, taking into account its wind generation, and so balance the grid. The country continues to expand the number of its interconnectors – a new 1.4 GW capacity submarine cable, able to transport the annual electricity consumption of approximately 2.7 million households – will be built between the UK and Denmark. The cable is expected to be operational by the end of 2022.
Obtaining accurate forecasts for wind and solar generation also helps grid operators to manage the system.
To balance the variability of wind and solar power, backup technologies are needed that can quickly ramp up or down, notes the report. Examples are gas-power stations, hydropower and power-to-heat. In Uruguay, where wind generation has grown more than 30-fold in the past five years, hydropower is used to balance power generation. The country also relies on its interconnectors with Brazil and Argentina when wind power is in surplus. Denmark and Germany redesigned their existing coal plants which are now able to start more quickly and run more flexibly.
Obtaining accurate forecasts for wind and solar generation also helps grid operators to manage the system. Spain has upgraded its national forecasting system, Sipreolico, which provides hourly wind production forecasts for up to 10 days ahead. As a result, it has managed to reduce its 24-hour prediction error, from 18% to 9% between 2008 and 2015.
So how far can the renewable energy share grow in the end?
The study did not seek to answer that question, says Gerard Wynn, a London-based IEEFA energy finance consultant and lead author of the report. It focused on real-world case studies – what countries are actually doing.
“The whole point was to cut through the academic debate about limits of possibility. What we show is that two countries/markets – South Australia and Denmark – have already achieved 50% share of variable renewables. That is 10 times the global average of 5.2%, which shows that most countries can grow their variable renewables a great deal without worrying about limits.”