The recent re-introduction of coal to Germany’s power mix is a clear sign that the country’s Energiewende program is under strain. The government’s reason for returning to this high carbon emitter? To ensure a more reliable flow of power from the national grid. This controversial move has environmentalists up in arms as they say the government has taken a huge step backward.
This ambitious long-term German program is enshrined in law. It aims to slash carbon emissions by replacing fossil fuels with renewable energy and is in many ways a resounding success, much to the world’s surprise (and cautious admiration).
While the country’s green energy portfolio continues to grow at an astonishing rate. Renewables account for over 25% of the country’s gross electricity needs and the government intends to increase that to 80% by 2050. This success is not without its challenges.
The variable nature of renewables delivers increasing power surges caused by the rapid rise and fall of wind and solar power. This has resulted in over 200,000 blackouts (lasting three minutes at a time) during 2011, according to Nature.com. Experts warn of larger and longer-lasting power failures if this problem is not resolved.
As the re-introduction of coal is not a long-term sustainable solution, three issues must be addressed in order to accommodate variable renewable power: power storage solutions, new demand response technology and a move to an agile and upgraded grid.
Power Storage Solutions
With electricity generally created on-demand, the electricity grid has no inherent storage capacity. This becomes problematic as renewable power grows. Renewable penetration exceeding 10% can cause serious stability issues for electricity networks, according to Daryl Wilson, CEO of Hydrogenics and Chair of the CHFCA. He explains that at this level, large-scale storage solutions are a necessity if renewables are to work.
“Renewable energy is a wonderful thing — provided you are able to store it at a large scale and distribute it efficiently,” explains Frithjof Staiß, managing director of the Center for Solar Energy and Hydrogen Research (ZSW) in Stuttgart, “By making renewable energy more manageable and marketable, advanced storage technologies can ultimately help to reduce the cost of wind and solar power.”
The intermittent nature of renewables definitely limits consumption. But, this limit can be circumvented if renewable energy is stored during times of excess production, thus buffering the effect of variability on the grid and providing a more predictable and reliable power supply. Storage will help to eliminate waste, both of energy and asset investment. In this area lie both legislative and technological challenges as our in depth look on prower storage will show.
Asset utilization for renewables is far below that of conventional systems and full potential cannot be realized until suitable storage mechanisms are in place. However, this is not the case with windfarms that have a generating capacity greater than 200MW, explains Andrew Jones, Managing Director of S&C Electric Europe Ltd, a power delivery solution provider. He says the technology is already proven as storage needs to be 10 to 15% of the wind farm capacity. Work carried out by Imperial College in the UK [Strategic Assessment of the Role and Value of Energy Storage Systems in the UK Low Carbon Energy Future-Report for the Carbon Trust June 2012] shows the real value of bulk storage for renewables is around 2 hours storage and after that although useful, it drops off. Successful technologies operating at this level globally already exist.
But, the fact remains as renewable generation tips to scales of over 50% - 60% as was recently reported energy storage, at this scale, is a significant technological challenge which cannot be satisfactorily met with existing technology.
The market is set to grow and surpass US$30-bn annually by 2022 according to a recent report by Navigant Research. Potential options include batteries, pumped hydropower, compressed air energy storage (CAES), flywheels, hydrogen, cryogenics, heat and fuel cells. However, the biggest problem with most energy storage options is a low energy density. Batteries, flywheels and compressed air are the least energy dense.
Pumped hydropower (currently being used in Germany) can store large quantities of power for long periods of time. This stored power can be accessed relatively quickly. However, the major drawbacks are high initial capital costs and location-technology is limited by geography (locations must be able to host a large reservoir at a significantly higher elevation than the power station.) CAES is also limited by geography as it generally requires an underground cavern which would store compressed air.
Batteries are often used in personal solar systems to provide power at night. But, because of their low energy density, batteries are very seldom used to back up power plants. They are also costly and have a limited lifespan. There is however, a great deal of research going in to the development of advanced batteries which are expected to reach GW levels of utility-scale storage over the next 10 years.
Experts say that Power-to-gas (P2G) technology is the best way to handle the unreliability of solar and wind power. It may be the solution that Germany, and other countries, is looking for. During sunny or blustery days, excess electricity is transformed into usable and storable hydrogen or methane gas via water electrolysis. Hydrogen is one of the more energy-dense storage options by weight. The hydrogen is then stored and burned to generate power when there is less wind and sun, adding much-needed flexibility to electricity grids, avoiding energy wastage and providing true financial benefits to operators. The advantages of hydrogen (as a clean energy carrier) include greater integration, flexibility and efficiency for power distribution, and the ability to link all forms of energy usage.
Demand Response Technology and Solutions
With cost-effective storage solutions still being developed, intermittency issues continue to pose a challenge for the energy industry. Automated Demand Response (ADR) is able to balance this renewable intermittency in a cost-effective way. When combined with grid power storage, it will assist utilities to manage the grid more effectively. ADR -an essential part of the smart grid-can decrease grid failures, relieve intermittency issues and reduce consumption during peak demand times.
Demand response (DR) is already being used to provide a backup service when there are issues with the grid. Examples of this include low energy production, a drop in renewables generation and transmission line damage. However, demand response has yet to reach its full potential. This is due mostly to regulatory concerns, payment structures and response time limitations. Independent system operators definitely see the growth of demand response as an excellent way in which to deal with the high penetration of renewables.
With technological developments and decreasing renewable energy prices, particularly wind and solar, demand response and renewables integration are both growing into significant factors in the short-term markets. demand response acts as a counterbalance against price volatility in the short-term power markets, while the integration of renewables means that weather fluctuations will increasingly affect the short-term price of power. According Pike Research, this will lead to accelerating growth in short-term power markets over the next several years.
Renewable sources require a new approach to demand response in order to accurately predict power surges. The good news is that this technology is already being developed. Exciting breakthrough renewable energy forecasting technologies are only two years away from revolutionizing the efficiency of wind and solar generation on the US power grid. Scientists and engineers are in the process of developing technology that will assist with predicting fluctuating energy levels from wind and solar. The renewable energy forecasting system is being designed to assist the utility with increasing renewable energy output to the grid and at the same time, ensuring a reliable power supply. Forecasts will inevitably reduce costs.
The forecasting technology will provide “probabilistic forecast which means that utilities can make decisions based on high-accuracy predictions of certain weather conditions which affect the level of power generated by wind and solar. Based on these predictions, utilities can increase or decrease base load generation in order to meet overall demand.
Electricity can’t yet be stored in large quantities so utilities have to draw power from coal or natural gas facilities to make up for low levels of renewable power generation. This results in more pollution and higher costs as the coal and gas generation units tend to be more expensive than renewables. Also, if these units are unavailable when needed, the utility has to buy power on the expensive electricity spot market. Experts believe that more detailed and accurate forecasts will result in major returns on investment. It will also make renewable energy more competitive in the marketplace.
The Imperial College report suggests that distributed storage is the most beneficial for the power grid. Germany has recently established a program where subsidies encourage the distribution of energy storage. The energy storage system is meant to be used in conjunction with distributed solar installations with German-made storage systems. In order to gain the subsidy, the maximum size requirement is 30KW and the batteries should have a warranty of at least seven years. Another requirement is that the PV installation must transmit 60% of its capacity to the grid over the lifetime of the plant. The battery subsidies will apply retroactively when connected to solar systems installed in 2013.
Germany’s goal is to generate clean, renewable energy and transport in every corner of the country. However, for this to work, Germany must expand and rebuild its grid-and fast. The grid must be able to accommodate new power sources transmitted from solar and biogas plants, as well as offshore wind farms (most are situated in the North and Baltic Seas). Most of Germany’s power will no longer be generated in power plants located close to major cities and towns. Progress has been slow. Approximately 1,550km (963 miles) of high-voltage power lines have yet to be erected and dozens of wind farms must still be connected [need citation / example] to the terrestrial power grid via new subsea cables, costing the country billions.
New DR and storage technology will need a grid that can support it. Existing infrastructure simply cannot handle these new innovations and will need to be upgraded to appropriate levels. The integration of renewables is causing disruption and calls for a smarter grid, one that consists of intelligent electronic devices that can communicate with each other in order to control power better. The smarter grid has to provide a balanced network in which electricity distribution is increasingly automated. The automated control of electricity generators and consumers is increasingly supply-focused. However, for smart grids to become a reality, new components have to be installed at all levels of the grid and existing processes must be re-assessed.
Germany has proven to the world that significant shifts to renewable power are possible. However it also shows that the grid and new technology and processes still do not work well together. It is key for the Enrgiewende to succeed that these issues are dealt with and they are a pointer to the challenges ahead for other countries wanting to embark on a similar journey.