Key to the large-scale development of renewable energy; Energy storage batteries

Energy storage technology is the key to solving the problem of the intermittent nature of renewable energy, the inability of the grid to absorb and connect on a large scale, and the bottleneck of charging facilities and battery safety for electric vehicles. There are three benefits of energy storage technology to the grid: First, it helps increase the penetration rate of renewable energy and promotes the development of distributed power generation; The second is to improve the stability of the grid and achieve adequate peak adjustment, reduce peak load and corresponding grid investment and power supply investment; Third, promote the liberalization of the electricity market through the design of electricity prices.

Generalized energy storage technologies include heat storage and electricity storage. In a narrow sense it is a technique that uses physical or chemical methods to store electrical energy and release it when needed. With the gradual increase of human energy demand, the constraints of traditional energy in terms of reserves, environmental pollution, energy efficiency and cost have become increasingly prominent. The search for energy alternatives and the research and use of new energy sources have become the common theme of the world and are also irreversible energy development trends in the future. From a narrow perspective, energy storage technology includes mechanical energy storage, battery energy storage, and electromagnetic energy storage. Among them, it is more mature. Commercially available applications include pumping energy storage and compressed air energy storage. These two are large-scale energy storage technologies. It is generally believed that the commercial application of battery storage energy is still faced with cost problems. Only a few high-tariff areas, combined with photovoltaic power generation, can energy storage technology be economically feasible. With the Advancement of technology, the cost of battery storage has indeed continued to decline, but it is generally believed that due to higher costs or other technical factors, it can not be used commercially on a large scale.

In recent years, the share of renewable energy in electricity generation has gradually increased. Not only is renewable energy seen as an effective solution to environmental problems, particularly carbon emission reduction, but in the long run it may be one of the most important solutions to human energy needs. The global share of renewable energy in electricity production in 2014 was 22.8 % (including hydropower, etc.), of which wind and solar energy accounted for 4 %. In the face of severe environmental pressure, China has attached greater importance to the development of renewable energy power generation. In 2014, the number of kilowatt-hours generated by renewable energy was 1.2 trillion, accounting for 22 % of the total power generation, of which connected wind power accounted for 2.8 % of the total power generation. Photovoltaics account for 0.45 % of total power generation, and grid-connected photovoltaics account for 0.42 %. In a joint statement issued by China and the United States in 2014, China proposed to peak carbon dioxide emissions by 2030 and strive to do so at an early date, and accordingly increase the share of non-fossil energy in primary energy consumption to 20 % by 2030. The previous plan was to account for 15 % of non-fossil energy by 2020. Taking into account the long construction period of hydropowerspecial power, growth is limited by endowment, and the development potential of wind and light is very large.

The breakthrough of battery energy storage system has reached a key point. Now studying the economics of energy storage is more time-sensitive and guiding than before. It is feasible and empirically relevant to carry out research and policy setting of renewable energy and energy storage systems step by step from macro and micro.

Importance of energy storage technology

At present, the main way to find new energy is to gradually integrate wind energy and solar energy into the power system and occupy an increasing proportion. Compared with traditional fossil energy power generation, renewable energy generation based on wind energy and solar energy depends on natural conditions and has the characteristics of volatility and intermittent. Large-scale integration will have a great impact on the security and stability of the grid. Some experts believe that for wind power generation, if the installed proportion is less than 10 % of the system, traditional technology can basically guarantee the security and stability of the power grid; When the proportion of wind power installed exceeds 20 %, energy storage means are needed to reduce volatility and intermittent, and to avoid unbearable shocks to the power grid. Therefore, the development of energy storage technology is an essential condition for large-scale grid connection of renewable energy generation.

For distributed renewable energy (wind, electricity, and solar), energy storage technology is more important. Distributed energy mainly refers to the energy supply mode built on the client side, which can be operated independently or in parallel with the network. A new energy system designed with demand response according to the user's various energy needs is a decentralized energy supply system that can maximize resources and environmental benefits. system. As it can reduce the loss of the transmission link, it can improve energy use efficiency. However, due to the instability of wind power and solar energy, energy storage means is also one of the necessary conditions for the large-scale development of distributed renewable energy. Some people think that by 2050, human solar energy can account for 50 % of total energy supply. Without economically viable energy storage technologies, this beautiful vision is difficult to imagine. Therefore, it can be said that energy storage technology can truly change the human energy supply.

Energy security is also an important goal of China's energy development. The dependence of China's oil imports is now more than 60 %, and it will continue to rise in the future. The large fluctuations in oil prices will not only affect the overall economic performance, but also affect the healthy development of the energy industry. Therefore, the government needs to arrange oil substitutes in advance, reduce energy dependence on other countries, and reduce the impact of international oil price fluctuations on the safe operation of the economy. Hybrid electric vehicles and pure electric vehicles are considered to be the main directions for the transformation and development of the automotive industry in the future. They have become the focus of development of the world's automotive powers and major automobile manufacturers, and energy storage technology is the main constraint of the development of electric vehicles. For China, in addition to reducing urban environmental pollution, the popularity of electric vehicles can also replace oil and reduce oil dependence. On the other hand, electric vehicles and energy storage technologies are powerful substitutes for oil. In the long run, the biggest threat to oil prices may be electric vehicles and energy storage technologies. Imagine if half the road was powered by electric cars, where would the price of oil fall?

Electric vehicles and energy storage technologies have made rapid progress in recent years, and the possibility of replacing oil has become more and more obvious.

After the development of lithium batteries in 1992, SONY has made great progress in materials and manufacturing processes, and has a wide range of applications in power generation systems and electric vehicles. In 2014, the world's new energy storage technology installed, lithium-ion batteries accounted for 71%. At present, lithium battery technology still can not meet the universal requirements of electric vehicles. First, because the battery is too large, the weight of electric vehicles generally exceeds that of a comparable gasoline car, but the endurance is only half that of gasoline cars. Secondly, lithium-ion batteries can't meet consumer demand in terms of charging. It is estimated that electric vehicles want to be commercialized, and the battery density is at least 250Wh/kg. However, the current lithium-ion battery density of electric vehicles is generally less than 100Wh/kg. Finally, the current cost of lithium batteries is too high, which can account for half of the cost of electric vehicles, which directly leads to the difficulty of competing with traditional cars in terms of price.

In April, Tesla launched Powerwall household energy storage batteries, which has attracted the attention of the industry. Powerwall can release electricity stored when the electricity bill is low, or use it with renewable energy (solar wind power). Its economy is the most important criterion for large-scale promotion. The Powerwall launched this time has 7kWh and 10kWh capacity, priced at $3,000 and $3,500, respectively, and provides 10 years of quality insurance, but there are limits on the number of charges. Since Powerwall mainly focuses on the use of products and solar power generation systems, in addition to batteries, users also need to purchase solar panels, inverters, etc. The entire system cost is said to be more than 20,000 US dollars. Since solar users can sell the remaining power to the grid, it weakens Powerwall's economy. At present, the total price of installed energy storage batteries in the United States is about 128 million U.S. dollars. Most of them are concentrated in business organizations, and household installations are only 1 %. Some organizations have analyzed that Tesla needs to cut sales prices by about 75 %. Tesla is working with Panasonic to build a large battery plant that is said to cut costs by about 30 % in the near future. Powerwall's costs do need to fall even more if oil prices remain low.

All the time, all countries in the world attach great importance to the development and application of large-capacity energy storage technology. At present, the United States has invested 95 energy storage projects and has an installed capacity of more than 357 MW. The installed scale of Japan is about 310MW, ranking second. This year's growth has been even more rapid. In 2014, the United States added 34.4 MW, and China and Europe ranked second and third, with 31 MW and 27.7 MW respectively. The commercialization of large-capacity energy storage technology is only sodium sulfur batteries and liquid-flow batteries. For example, sodium sulfur batteries have a higher energy storage density, an efficiency of about 80 %, and the number of charge and discharge can reach more than 6,000 times. The sodium sulfur battery energy storage system developed by Japan's Kyocera Corporation has more than 100 units in operation and has a capacity of more than 100 MW. At present, the proportion of sodium and sulfur batteries installed in large capacity storage capacity is the largest, reaching 40 %, but the high cost of sodium and sulfur batteries is an important factor that restricts its development.

How far away is the energy storage technology?

In the process of low-carbon transformation, renewable energy development has provided mankind with a clean and sustainable source of energy, while the rise of electric vehicles has provided the possibility of large-scale oil substitution. Therefore, the global energy supply mode will face tremendous changes. But both renewable energy and the massive development of electric cars face the same dilemma: energy storage technology.

Renewable energy has a discontinuous character, the grid can not be integrated on a large scale, and electric vehicles face bottlenecks in charging facilities and battery safety, and energy storage technology is the key to solving these problems. The benefits of energy storage technologies for the grid are threefold. First, it helps increase the penetration rate of renewable energy and promotes the development of distributed(micro-grid) power generation; The second is to improve the stability of the grid and achieve adequate peak adjustment, reduce peak load and corresponding grid investment and power supply investment; Third, promote the liberalization of the electricity market through the design of electricity prices. More importantly, battery storage is a crucial bottleneck in the development of distributed(micro-grid) systems.

The importance of energy storage technology to the development of electric vehicles is relatively intuitive. Charging, cruising miles and safety issues for electric cars all involve batteries. For example, safety accidents caused by batteries have weakened consumer confidence and affected the development of electric cars. For China, the development of electric cars, in addition to oil substitution, can also solve urban car exhaust and noise pollution. Using electric peaks and valleys, electric vehicles can also use night excess and cheap electricity to charge at night.

Tesla's Powerwall, an energy storage device for home users, and Powerpack, a power grid device, have been priced as low as $350 per kilowatt-hour. Powerpack has not given specific technical parameters, but some media have reported that the cost is only US$ 250 per kilowatt-hour, which means that energy storage technology is beginning to be economically attractive.

The Xiamen University Energy Economy and Energy Policy Collaborative Innovation Center recently conducted a study to use Tesla's Powerwall and Powerpack to establish an optimized arbitrage model for China's current peak price policy, and to analyze the energy storage investment returns and external impacts of provinces. Analysis, Quantitative analysis of the impact of various influencing factors on the investment income level of energy storage. The basic idea is to start from the perspective of power grid, so that the energy storage system can fully play the role of peak adjustment, and then determine the economy and investment income of energy storage technology.

Electricity transmission and distribution is mainly invested and operated by the National grid and the southern grid, while electricity prices are set by the NDRC based on the cost of grid companies combined with regional development. Due to different resource endowments, geographical conditions and economic development levels, there are large differences in electricity prices in each province. At present, many provinces that import electricity have implemented peak and valley tariff policies, that is, different peak and valley tariff rates, encouraging consumers to increase power consumption during off-peak hours, save electricity at peak times, and facilitate the balanced supply of electricity.

Through the economic evaluation of energy storage investments in different regions, it was found that some regional energy storage investments have been able to achieve returns. Without subsidies, investment in energy storage can be profitable, and the level of income is affected by the price difference. It is also related to the division of peak and valley time periods. The economy of energy storage technology can be greatly improved if we consider how pricing can make the energy storage system fully play the role of peak adjustment from the point of view of power grid. The research results also show that when the optimal scale of energy storage investment is reached, the load of the power grid will be more balanced, and power plants can also operate in a more stable and efficient mode. Therefore, there will be great room for development in terms of investment potential.

Obviously, the current study is still very shallow. Due to various restrictions, it is not possible to fully consider the factors that affect the battery economy. For example: First, due to certain losses in the process of power storage and conversion, its proportion in total power consumption is not large, considering the effect of increasing power source and power grid operation efficiency. Therefore, the impact of large-scale energy storage on carbon emissions needs further analysis. Second, energy storage can reduce the externalities of grid investment and power investment. How these externalities are evaluated quantitatively and quantitatively, and how to compare with the cost of energy storage, will be a very significant issue. However, it is relatively certain that if the environmental externalities are fully considered, the economy of energy storage technology will likely increase significantly.

For the power grid, the development of battery energy storage technology may fundamentally solve the instability of renewable energy power generation, expand the share of renewable energy power generation on a large scale, and effectively improve the connection rate and system stability. For the government, adopting more targeted and differentiated tariff policies will not only help promote the profitability of battery storage technology, but also optimize the allocation of power resources and improve the overall power generation efficiency of power systems.

There are also significant limitations to the study, as there is no assessment of the impact of the development of energy storage technologies on increasing renewable energy penetration and on the development of distributed and microgrids. It can be said that research is still difficult to prove the effectiveness of current energy storage technologies, but simply to see how far away energy storage technology is from us. But such exploratory research is important, because if energy storage breaks out, the world's energy markets could change dramatically, making our energy consumption cleaner and our power grids and power plants more efficient. The share of renewable energy use could also be significantly increased. Since these changes are only just beginning, the effects of these changes are not directly felt and are therefore easily overlooked.

Battery storage is the key to large-scale development of renewable energy

With the world's largest demand for electricity and the world's largest generator of renewable energy, China plays an important role in global renewable energy development. The biggest problem in the development of renewable energy power generation is the intermittent and unpredictable nature of renewable energy generation. On the one hand, there is inconsistency between the power generation concentration period of renewable energy and the power generation period. The peak of wind power generation is generally concentrated at night, and the peak of solar power generation is concentrated during the day. The power curve of industrial electricity is relatively gentle, and residents use electricity at two peaks during the day and at night. In addition, with the change of seasons and weather, renewable energy generation and electricity consumption curves will change accordingly. Most of the country's wind power output in the spring is the largest; The output of photovoltaic power generation is the highest in the summer, and power generation is unpredictable with dramatic changes in weather.

These are trouble for the grid. The traditional solution is mainly concentrated in two solutions: First, the use of more flexible power generation facilities to cooperate with it to form a stable total output, and the more widely used is the combination of natural gas power generation and renewable energy power generation. The second is to store the energy of renewable energy generation. The traditional method of energy storage is to convert it into heat energy and other forms, such as the combination of heat storage and hot water systems with renewable energy power generation systems. The power storage method that does not involve energy conversion. In the past, it was mainly used as a pumping storage power station.

Neither of the above two schemes can fundamentally solve the problem of maintaining the stability of the grid after renewable power generation reaches a certain scale. The first method has two main limitations: First, it is not widely used and is more used in distributed systems; The second is related to fuel price factors, costs can not be controlled. The main limitation of the second approach is that when a pumped storage plant works, its energy source is also fundamentally derived from fossil energy. Therefore, although pumping storage energy helps to reduce the volatility of the grid, it does not have the inherent benefit of saving energy and reducing emissions. In addition, the application of pumped storage power station is affected by many factors such as location, cost and benefit distribution.

Thus, in the longer term, battery storage may be the most effective economic solution to the instability of renewable energy generation. The advantage of battery storage is that it can be large or small, and it is easy to combine with renewable energy power generation of all sizes; Charge and discharge fast, direct electricity and electric conversion, high conversion efficiency. The biggest factor of its limitation is economy, and the charge and discharge efficiency, safety, and life associated with cost. Traditionally, it has been thought that the high cost of battery storage is difficult to operate commercially.

This situation is changing rapidly. Recent breakthroughs in battery technology have made large-scale battery applications such as electric vehicles more common, and attempts to directly combine battery storage with power systems have begun. Tesla's PowerWall and Powerpack, with a single peak power of 3 kW, can store 10 kWh of electricity, charge and discharge energy efficiency of 92 %, can be further expanded to 1000 times through simple splicing. Tesla hopes to use this to change the human power model, set off an energy revolution, and promote the popularization of renewable energy. It now seems that Tesla is not bragging.

For systems with renewable energy and energy storage, the importance of energy storage strategy to system economy may be higher than the cost of energy storage equipment itself. Therefore, while vigorously promoting the development of energy storage equipment, the government should also advocate the integration of battery storage with renewable energy for power generation, actively set up pilot projects, and support pilot projects for the combination of renewable energy and energy storage systems, so as to find the best fit for China in practice. The most suitable energy storage strategy for the installation site of the project will lay a good foundation for the use of large-scale renewable energy power generation in the future.

Distributed photovoltaic projects combined with industrial power use may be the easiest to intervene in battery storage and the most profitable subject. In order to achieve the optimal economic benefits of the system combined with renewable energy and energy storage, the key lies in the effective prediction of renewable energy power generation. Therefore, while vigorously developing wind energy and photovoltaic, the government should also establish a platform to update and share relevant power generation and climate data in a timely manner, and provide effective power generation forecast information.

For the power grid, the development of battery energy storage technology may fundamentally solve the instability of renewable energy power generation, expand the share of renewable energy power generation on a large scale, and effectively improve the connection rate and system stability. For the government, adopting more targeted and differentiated tariff policies will not only help promote the profitability of battery storage technology, but also optimize the allocation of power resources and improve the overall power generation efficiency of power systems.

Conclusions and policy recommendations

As a key link in the development of new energy sources and electric vehicles, the technological breakthrough will change the energy pattern of the whole world. It can be said that energy storage technology is the key to the new energy era. Once energy storage technology is economically feasible, it will open a door to the new energy era for mankind. For China, the effective combination of electric vehicles, energy storage technology and wind power and solar energy, in addition to clean development, can also form an effective alternative to oil and ensure energy security. Therefore, the government should pay attention to the development of energy storage technology. For the traditional energy enterprises, it is necessary to pay attention to the development of energy storage technology and its interests. Its importance is self-evident.

Therefore, the thirteenth five-year energy strategic plan needs to focus on technological innovation in clean energy, electric vehicles and energy storage, as the cost reductions resulting from technological innovation are firm, reliable and permanent. Governments should make energy storage technology innovation, oil substitution and clean energy development an integral part of energy security.

It can be seen that energy storage technology can not be ignored. The technological advances of recent years have led to the gradual evolution of energy storage technologies. In the foreseeable future, the technological feasibility and economy of energy storage technologies will be further enhanced by technological advances. This change will likely profoundly affect the world's energy supply methods and energy structure. This will have a huge impact on traditional energy companies and our way of life.

For the development of renewable energy and the economy of energy storage technology, China has certain advantages. First, electricity prices are the core of renewable power generation and energy storage profits. Power prices are determined by the government. The government can set power peaks and differential electricity prices that are conducive to the development of renewable energy and energy storage technologies. Second, as a major producer of renewable energy, China has huge market potential and can provide economies of scale for renewable energy development and investment in energy storage technologies.

It should be recognized that battery storage technology is as important as the promotion of renewable energy for power generation. With the Advancement of technology, the cost and technology of battery energy storage have gradually entered the economic area. As a major producer of renewable energy, the government should strengthen its support for the research and application of battery energy storage technology, so as to seize the opportunity of the new energy revolution. In order to avoid a step behind, the Chinese government should seize the opportunity that energy storage technology is on the eve of a breakthrough, take advantage of the industrial scale and market advantages, promote the integration of battery storage energy research and industry of various technologies, and strive to achieve the large-scale application of battery storage energy as soon as possible.

The page contains the contents of the machine translation.