Renewable Questions and Answers, Part 2

    Having considered in the first part those issues related to renewable energy sources (RES), which until recently were considered to be a serious barrier to their development, but were later removed or weakened, we approached the problems of renewable energy that are still relevant today.

    Floating Chinese solar power plant

    Y: The fundamental variability and uncontrollability of the generation of renewable energy sources limits their share in the power system to 10-20%, after which accidents and blackouts begin.

    A: Initially, all large-scale electrical networks have the ability to adjust production and demand - on a scale of 5-10% in minutes and on a scale of 30-70% during the day. Automation of this process allows you to seamlessly embed small portions of RES-generation in the network, for example, 10% of the annual output in lumped sources, or 20% distributed throughout the network.

    With a further increase in the penetration of changeable renewable energy sources, problems begin to grow, since the compensatory capabilities of controlled generators are depleted.

    The share of RES-generation in Germany by year. About 6-7 percentage points here is hydropower and another about 5% - thermal power plants on biomass.

    To the penetration share of changeable renewable energy sources in 25-30% of the total annual consumption, however, there are enough technical solutions: the introduction of weather forecasting systems (= generation of renewable energy sources) to the dispatch office, the modernization of thermal power plants to increase the rate of change of power, the addition of new transmission lines and substations to increase the potential for power flows.

    Thus, in Germany, with an increase in the share of changeable renewable energy sources from 8 to 20% from 2010 to 2015, the average power outage per subscriber almost did not change - from 11.5 to 12.2 minutes per year (ie, 2 thousandths of a percent of time) . However, the cost of this stability has increased significantly, as we will discuss in the relevant section.

    You can say a few words about the technical side of things. Traditionally, the balancing of the power grid was based on two points - synchronous rotation of all generators in the network, which contributed decent inertia and insensitivity to rapid load changes and active power control, which made it possible to regain slow and large-scale load changes (for example, day-night).


    Renewable energy generation, for example, solar, does not have inertia, but it has the ability to synthesize the necessary network frequency, source resistance (i.e. given current) and reactive characteristics. Modern wind generators, in addition, can use the inertia of the wind turbine rotor to synthesize the necessary inertia of the network, although this technique is not widely used yet.

    Together with constant communication channels with management software controllers RES-network can theoretically support the smooth operation of the grid, but by virtue of a certain novelty of this phenomenon and the complexity of the phenomenon problems remain (for example large-scale blekaut in Australia in February 2017 was due to violations of the correct interaction of networks, wind power and heat power)

    It can be said carefully that while the rate of implementation of renewable energy sources is not very high, resting on the cost of switching the country's energy system to renewable energy sources, technical problems are insignificant - the network economy and dispatching manage to adapt to the existing situation.

    W: To balance the variability of renewable energy, incredible amounts of electricity are needed — hundreds of times more than their annual production today. So, balancing and impossible.

    A: Accumulation is the logical, easiest way to deal with changeability - we accumulate energy on weather excesses and spend on shortcomings. For the sun in successful places (where low LCOE of primary electricity panels) daily accumulation gradually goes from the laboratories to the field - the first projects appear (for example, a couple of dozen of such projects already) with panels of tens of megawatts, batteries of tens and hundreds of megawatts * hours - in the simplest case, “always beautiful weather” is enough for round-the-clock supply of consumers with a capacity of about 25-30% of the installed SS power.

    Problems begin if we try to extend the continuous supply of electricity for “one beautiful summer sunny day”

    Changes in the theoretical output of the SAT module during the year (day of the year along the lower axis) depending on the latitude of the installation.

    Indeed, already at the first glance at the annual schedules of renewable energy generation, their seasonality becomes visible, for solar power plants in Germany, say, reaching 30-fold (!) Difference between the summer peak and the winter minimum. This means that you need to either build an impressive excess of renewable energy generation (7 or maybe 10 times), or be able to store summer energy for the winter.

    The weekly schedule of production of renewable energy sources in Germany in 2017. The difference in the sun between the worst week (51) and the best (22) reaches 53 times.

    In the seasonal storage scenario, the sizes of batteries for temperate countries make up a few percent of the annual energy consumption for the extent of the share of renewable generation in the region of 60-85%. A few percent for Germany, for example - it is 10..15 TWh *, despite the fact that the global production of lithium-ion batteries today is about 0.25 TWh per year. Even bigger is the numbers for the United States and China - it can be about 50 ... 200 Twt * h. Moreover, these figures are optimized for some mix of variability, because for example, in the case of germanium, the anticorrelation of the seasonality of wind and sun (visible on the graph above) plays to reduce the size of accumulation.

    On the other hand, there is nothing fundamentally impossible in these figures - lithium on the planet is enough for building such quantities of mega-batteries, mankind is also able to build factories. Questions causes the price of such a decision, but more on that below.

    A little better is the situation with the possible storage of electricity in pumped storage power plants (PSPPs) - here you can find a lot of natural and artificial formations that allow you to store the required amounts of electricity, but such places are scattered around the planet extremely uneven, and if large countries, such as the United States, are likely to cope Since the issue of accumulation without increasing the production of lithium-ion batteries by a factor of 1000, it is possible in Europe to create a similar volume of PSPPs and this will not work.

    Solar-hydro-accumulating projects are actively developing in Chile.

    Finally, for solar power plants there is a variant of solar-thermal power plants with a heat accumulator - this technology is developing and promises round-the-clock electricity at an affordable price, but today its prospects are not completely clear. If energy storage issues become sharper as the share of renewable energy grows, then perhaps part of them will be removed with the help of SES heat accumulators .

    So far, balancing issues are trying to be resolved in a compromise way - by expanding the compensating capabilities of other types of electric power generators, building special “peak” gas power stations, building local batteries, demand for “24-hour renewables” - all this activity slightly increases the allowable share of uncontrolled generation in electrical system.

    In the future, apparently, the number of energy storage projects will increase, but it will be a very long time before any systematic and systemic importance appears due to the huge gap between the current scale of implementation and theoretical needs.

    W: No one takes into account the real cost of balancing the variability of renewable energy sources in the power system. When this cost comes up, plans for the introduction of renewable energy will collapse.

    A: I have already mentioned above that up to the share of changeable renewable energy sources in 10-20% of the costs are covered by the laid-in compensatory mechanisms of the power grids, therefore they are invisible. However, when this bar is exceeded, they begin to grow.

    The permissible share of alternative sources can be increased by traditional methods - by introducing the forecast of RES-generation for hours and days ahead, by increasing the maneuvering properties of controlled generation (thermal, nuclear and hydroelectric power plants), by increasing the number of connections in the network, managing (if possible) the demand for electricity. The cost of these solutions, according to the study (M. Joosa, I. Staffellb, 2018) is quite substantial - network costs in Germany and Britain rose by + 60% with an increase in the share of changeable renewable energy sources from 8 to 20% and from 3 to 14%, respectively. Here we must understand that the cost function is extremely non-linear - the bulk of the costs are accounted for by the moments when the compensation possibilities of the power grid approach the limit. This moment is well illustrated by such a picture.


    Here the costs of German electric grid operators for balancing changeable wind are expressed in euros. In 2012, they spent 200 million euro for 50 TWh (4 euro per MWh - a few percent of LCOE wind), and in 2015, when there was an unusually large amount of wind - 1100 million euro for 80 TWh / h, t. e. 13.75 euros per MWh - more than 20% of LCOE wind in Germany in 2015.

    The situation can be illustrated as follows: as the share of renewable energy grows, system costs increase and if the LCOE of renewable energy decreases with an increase in their volumes, the system LCOE first decreases, and starting from a certain share gives way to growth, and this growth accelerates

    Accelerating the growth of system LCOE with an increase in the share of renewable energy can be explained in fairly obvious details (a large proportion of renewable energy is not accepted by the system as superfluous, the conventional generation capacity drops, more and more networks need to be built, etc.), but in general this can be explained more generally: the old structure of the power system is becoming less and less optimal for renewable energy and it is necessary to build a new, already optimized for a large share of renewable energy. Since construction is very expensive (we can talk about a few annual GDP of a country), then it should be stretched for decades. And all these decades, the power system will operate in a non-optimal mode, i.e. medium term system LCOE will be higher than long term. This is both good and bad news for RES fans - for one thing,

    You can estimate the size of these costs from above - for example, 10 TW * h of lithium-ion batteries will cost (at a slightly promising cost) a trillion dollars, the construction of transcontinental power lines in Europe of 200 GW scale will be another trillion dollars, and the construction of a terra-Watt wind turbine - another two trillion and etc.

    Thus, the following gradation is obtained: 10-20% of RES-generation today can afford almost all countries, and the southern and rich or located in unique places - can afford more and more in cost, equal to or less than the traditional generation.

    A 40-50% share, if countries with predominant hydro or geothermal generation can fold, countries rich or uniquely located can afford to themselves - Germany, Denmark (which already has almost 50%), Great Britain, California (considering it a separate country) , Texas and also such countries as Saudi Arabia, the United Arab Emirates, Kuwait and other flood monarchies.

    A further increase in the share of renewable energy in these countries will require a radical restructuring of the networks and will drag on for a very long time, going beyond the horizon of reliable inertial forecasting.

    U: Well, okay, okay, everything is somehow very confusing, but what are the prospects for renewable energy sources? Will they win all other sources or not?

    A: The question requires knowledge of the future, which I do not possess. But if you look at the forecasts of various companies, you can see that optimists (Bloomberg NEF) believe that by 2050 the share of changeable renewable energy sources will reach 48% in electricity (approximately 24% in primary), and pessimists (British Petroleum), that ~ 30 % (15%) with today's share of ~ 10% in electricity production and about 4.5% in the production of primary energy.

    The Bloomberg forecast refers to the production of electricity (40-50% of the total primary energy consumption, the proportion will increase) The

    BP forecast covers the primary energy consumption, so the share of renewable energy here looks smaller and is divided into several scenarios.

    In my opinion, these inertial, compromise predictions can be safely thrown into the garbage - in any case, the smooth line that is drawn between today and 2050. The development of renewable energy will be determined by many factors - whether new low-cost batteries will appear (at a price of $ 50 per kilowatt * battery hour the 24-hour one-day price of the sun will be equal to gas / coal in most countries of the world), whether “end of hydrocarbons” or new things, such as shale / deep-sea oil, or global warming will become too obvious to let it down on the brakes ... In the other direction, the loss of popularity of “green” subjects, fatigue of voters on the costs of “energy turn-over”, economic difficulties stagnating energy consumption.

    Another forecast for batteries from BNEF - 1291 GW (* h?) Batteries installed by 2050, of which 40% locally in homes with SB, $ 70 per kilowatt * hour battery module (today this price is about $ 200).

    In the end, history knows a lot of unjustified energy forecasts - for example, forecasts for the development of nuclear energy in the 60s differed about ten times from reality, or forecasts 15 years ago for the development of renewable energy in Spain by 2020 - twice.

    The only thing that can be predicted is that until 2050 the situation in the world will definitely not comeabsolute dominance of renewable energy sources, although Bloomberg NEF for renewable energy + hydro gives a forecast of 64% of total electricity production (which corresponds to approximately 30-32% of primary production - today approximately equal amounts are occupied by coal, gas and oil). Only by the end of the 21st century, inertial forecasts give an almost complete transition to renewable energy sources, but it is absolutely impossible to predict the probability that this will be the case.

    W: And what about the technological breakthrough, new solar panels or super-batteries - what are the prospects here? Maybe there is something on the horizon?

    A: The search for innovations in the field of renewable energy and energy storage in the last 10-15 years has given very serious financial and human resources. However, the competition among scientific groups in this large field is extremely fierce. Groups are forced to promote their discoveries, so every week you can hear about another breakthrough in the field of batteries, or a little less often in the field of renewable energy generation.

    The development of lithium-ion batteries can be illustrated by the growth of the specific energy intensity (W * h per kilogram). Although the points are zafityy exponential, the forecast rectangle rather indicates continuous growth by 2030 (by 1.66 times). Although the specific energy consumption is not directly related to the cost, it affects it - less materials per kWh - less price.

    However, unbiased statistics show that the number of patents issued in this field is decreasing after a peak in 2015. The dominant position of polycrystalline silicon SB on the market today (while 10 years ago 4-5 different technologies had equal shares) and 2-3 very similar design types of wind turbines hinted that technological consolidation of RES was completed. This, in turn, means that the laboratories have not yet found options that would promise a breakthrough from the current level, and the main manufacturers have switched from exploratory research to optimizing, where it is more difficult to get a new patent.


    Here plays another factor. For many years, the cost of semiconductor panels dominated the price, for example, of solar electricity. However, during the boom years, this cost fell so much that the share of the “semiconductor part” fell to <50% of the total cost of the SES. A further price reduction has lost its former strength, and does not have such an effect on LCOE, which means it is no longer so much in demand by the market.

    2018 in this graph is a forecast that is not yet justified, the price is frozen at the level of 16-17 years, which can also be considered an important point in the development of technology

    Does this mean that now we are waiting for a dismal evolution, when 10% improvement in efficiency over 10 years is considered a super cool result? Such a situation is likely. However, unlike civil aviation, there remains a chance that some new technology will “shoot”. For example, it would seem that reducing the price of panels by 10 times does not make sense for LCOE? But this means a strong simplification of the issue of accumulation and balancing - now for the same money it will be possible to install a huge excess of panels that simply will not work in the summer and still provide sufficient power in the winter.

    The future is not known, but solid state physics / engineering is still fairly regular with surprises, so it’s too early to discard this option. The only thing that can be said is that even if such a revolution occurs, it will affect the global trajectory of the introduction of renewable energy sources not earlier than in 10 years, but will completely turn over all forecasts in 15-20 years.

    If we take battery technologies, here the balance, on the contrary, is biased in favor of the probability of revolutionary shifts, since there are many promising areas of development and a big gap between the theoretical possibilities of lithium and reality. In the foreseeable future, quite good specific growth of battery characteristics is possible. It is also likely to reduce the cost per kilowatt * hour, which greatly expands the area of ​​competitiveness of renewable energy.

    Summarizing, we can say that the onset of renewable energy generation will continue in the coming decades, at a more or less rate, and this type of generation will become more and more competitive and competing every year. At the same time, it can be expected that the exponential growth of installed capacity in the next decade will become linear due to the slowdown in technical and economic progress of renewable energy sources, therefore mid-century forecasts made on the basis of extrapolation exponents will most likely fail.

    Also popular now: