Jacobson has studied how wind, water and solar technologies can be integrated to provide the majority of the world's energy needs. Because the wind blows during stormy conditions when the sun does not shine and the sun often shines on calm days with little wind, combining wind and solar can go a long way toward meeting demand, especially when geothermal provides a steady base and hydroelectric can be called on to fill in the gaps.
Delucchi and Mark Z. Jacobson argue that there are at least seven ways to design and operate renewable energy systems so that they will reliably satisfy electricity demand: Studies by academics and grid operators indicate that the cost of compensating for intermittency is expected to be high at levels of penetration above the low levels currently in use today    Large, distributed power grids are better able to deal with high levels of penetration than small, isolated grids.
Matching power demand to supply is not a problem specific to intermittent power sources. Existing power grids already contain elements of uncertainty including sudden and large changes in demand and unforeseen power plant failures. Though power grids are already designed to have some capacity in excess of projected peak demand to deal with these problems, significant upgrades may be required to accommodate large amounts of intermittent power.
Again, it has to be noted that already significant amounts of this reserve are operating on the grid due to the general safety and quality demands of the grid. Wind imposes additional demands only inasmuch as it increases variability and unpredictability.
However, these factors are nothing completely new to system operators. By adding another variable, wind power changes the degree of uncertainty, but not the kind A pumped storage facility would then store enough water for the grids weekly load, with a capacity for peak demand i. This would allow for one week of overcast and windless conditions.
There are unusual costs associated with building storage and total generating capacity being six times the grid average. All sources of electrical power have some degree of variability, as do demand patterns which routinely drive large swings in the amount of electricity that suppliers feed into the grid.
Wherever possible, grid operations procedures are designed to match supply with demand at high levels of reliability, and the tools to influence supply and demand are well-developed. The introduction of large amounts of highly variable power generation may require changes to existing procedures and additional investments. The capacity of a reliable renewable power supply, can be fulfilled by the use of backup or extra infrastructure and technology , using mixed renewables to produce electricity above the intermittent average , which may be utilised to meet regular and unanticipated supply demands.
All managed grids already have existing operational and "spinning" reserve to compensate for existing uncertainties in the power grid. At times of low load where non-dispatchable output from wind and solar may be high, grid stability requires lowering the output of various dispatchable generating sources or even increasing controllable loads, possibly by using energy storage to time-shift output to times of higher demand.
Such mechanisms can include:. Storage of electrical energy results in some lost energy because storage and retrieval are not perfectly efficient. Storage may also require substantial capital investment and space for storage facilities. The variability of production from a single wind turbine can be high.
Combining any additional number of turbines for example, in a wind farm results in lower statistical variation, as long as the correlation between the output of each turbine is imperfect, and the correlations are always imperfect due to the distance between each turbine. Similarly, geographically distant wind turbines or wind farms have lower correlations, reducing overall variability. Since wind power is dependent on weather systems, there is a limit to the benefit of this geographic diversity for any power system.
Multiple wind farms spread over a wide geographic area and gridded together produce power more constantly and with less variability than smaller installations. The ability to predict wind output is expected to increase over time as data is collected, especially from newer facilities.
In the past electrical generation was mostly dispatchable and consumer demand led how much and when to dispatch power. The trend in adding intermittent sources such as wind, solar, and run-of-river hydro means the grid is beginning to be led by the intermittent supply.
The use of intermittent sources relies on electric power grids that are carefully managed, for instance using highly dispatchable generation that is able to shut itself down whenever an intermittent source starts to generate power, and to successfully startup without warning when the intermittents stop generating.
The displaced dispatchable generation could be coal, natural gas, biomass, nuclear, geothermal or storage hydro. Rather than starting and stopping nuclear or geothermal it is cheaper to use them as constant base load power. Any power generated in excess of demand can displace heating fuels, be converted to storage or sold to another grid.
Biofuels and conventional hydro can be saved for later when intermittents are not generating power. Alternatives to burning coal and natural gas which produce fewer greenhouse gases may eventually make fossil fuels a stranded asset that is left in the ground.
Highly integrated grids favor flexibility and performance over cost, resulting in more plants that operate for fewer hours and lower capacity factors. Penetration refers to the proportion of a primary energy PE source in an electric power system, expressed as a percentage.
The penetration can be calculated either as: The level of penetration of intermittent variable sources is significant for the following reasons:.
There is no generally accepted maximum level of penetration, as each system's capacity to compensate for intermittency differs, and the systems themselves will change over time. Discussion of acceptable or unacceptable penetration figures should be treated and used with caution, as the relevance or significance will be highly dependent on local factors, grid structure and management, and existing generation capacity.
For most systems worldwide, existing penetration levels are significantly lower than practical or theoretical maximums; for example, a UK study found that "it is clear that intermittent generation need not compromise electricity system reliability at any level of penetration foreseeable in Britain over the next 20 years, although it may increase costs.
There is no generally accepted maximum penetration of wind energy that would be feasible in any given grid. Rather, economic efficiency and cost considerations are more likely to dominate as critical factors; technical solutions may allow higher penetration levels to be considered in future, particularly if cost considerations are secondary.
Studies have been conducted to assess the viability of specific penetration levels in specific energy markets. A series of detailed modelling studies by Dr. The report states that "electricity transport proves to be one of the keys to an economical electricity supply" and underscores the importance of "international co-operation in the field of renewable energy use [and] transmission.
Czisch described the concept in an interview, saying "For example, if we look at wind energy in Europe. We have a winter wind region where the maximum production is in winter and in the Sahara region in northern Africa the highest wind production is in the summer and if you combine both, you come quite close to the needs of the people living in the whole area - let's say from northern Russia down to the southern part of the Sahara.
The study cautions that various assumptions were made that "may have understated dispatch restrictions, resulting in an underestimation of operational costs, required wind curtailment, and CO 2 emissions" and that "The limitations of the study may overstate the technical feasibility of the portfolios analyzed Scenario 6 proposed the following mix of renewable energies:.
The study found that for Scenario 6, "a significant number of hours characterized by extreme system situations occurred where load and reserve requirements could not be met. The results of the network study indicated that for such extreme renewable penetration scenarios, a system re-design is required, rather than a reinforcement exercise.
Estimates of the cost of wind energy may include estimates of the "external" costs of wind variability, or be limited to the cost of production. All electrical plant has costs that are separate from the cost of production, including, for example, the cost of any necessary transmission capacity or reserve capacity in case of loss of generating capacity.
Many types of generation, particularly fossil fuel derived, will also have cost externalities such as pollution, greenhouse gas emission, and habitat destruction which are generally not directly accounted for. The magnitude of the economic impacts is debated and will vary by location, but is expected to rise with higher penetration levels.
At low penetration levels, costs such as operating reserve and balancing costs are believed to be insignificant. Intermittency may introduce additional costs that are distinct from or of a different magnitude than for traditional generation types.
Studies have been performed to determine the costs of variability. National Grid notes that "increasing levels of such renewable generation on the system would increase the costs of balancing the system and managing system frequency. The study classified "Intermittency" as "Not a significant issue" for the target but a "Significant Issue" for the target. There are differing views about some sources of renewable energy and intermittency.
The World Nuclear Association argues that the sun, wind, tides and waves cannot be controlled to provide directly either continuous base-load power, or peak-load power when it is needed. For many years there was a consensus within the electric utilities in the U. Thomas Petersnik, an analyst with the U. Energy Information Administration put it this way: The uncorrected for their intermittency "unbuffered" EROEI for each energy source analyzed is as depicted in the attached table at right,   while the buffered corrected for their intermittency EROEI stated in the paper for all low carbon power sources, with the exception of nuclear and biomass, were yet lower still.
Supporters say that the total electricity generated from a large-scale array of dispersed wind farms , located in different wind regimes, cannot be accurately described as intermittent, because it does not start up or switch off instantaneously at irregular intervals. Typical hydroelectric plants in the dam configuration may have substantial storage capacity, and be considered dispatchable.
Run of the river hydroelectric generation will typically have limited or no storage capacity, and will be variable on a seasonal or annual basis dependent on rainfall and snow melt.
Amory Lovins suggests a few basic strategies to deal with these issues:. Moreover, efficient energy use and energy conservation measures can reliably reduce demand for base-load and peak-load electricity. Methods to manage wind power integration range from those that are commonly used at present e. Improved forecasting can also contribute as the daily and seasonal variations in wind and solar sources are to some extent predictable.
From Wikipedia, the free encyclopedia. Interconnect geographically dispersed, technologically diverse renewable generation types such as wind, solar, and tidal to smooth out daily supply variability. For example, solar power generation is highest at midday, and wind is often strongest at night and early morning. The combined solar-wind resource has lower variance than either individual source. Use dispatchable renewable energy generators such as hydroelectric, geothermal, and biomass to fill energy deficits between demand and intermittent resource generation.
Use demand response or demand-side management to shift flexible loads to a time when more renewable energy is available, and away from times when renewable generation is low.
This requires that loads be capable of receiving and responding to price or control signals from the local utility or grid operator. Store excess renewable power, which would otherwise be curtailed, for later use at times when generation is not sufficient to meet load. Some energy storage technology types include pumped hydro, electrochemical batteries, flywheels, compressed air, and hydrogen.
Customer-sited storage is typically used to increase self-consumption of distributed energy resources such as photovoltaic panels, to shift grid power consumption towards off-peak hours, and to reduce demand charges. Over-size renewable peak generation capacity to minimize the times when available renewable power is less than demand, and to provide spare power to produce hydrogen for flexible transportation and heat uses.
Use electric vehicles as an additional storage resource. A further development, known as V2B vehicle-to-building , sees bidirectional power flow into the vehicle at optimal times, and out of the vehicle to meet building demand. The most advanced form, known as V2G Vehicle-to-grid , sees power exported from the EV back on to the grid when needed.
Forecast the weather winds, sunlight, waves, tides and precipitation to better plan for energy supply needs. National Grid Reserve Service. HVDC and Super grid. Renewable Electricity and the Grid and Energy security and renewable technology. Department of Communications, Energy and Natural Resources.
Archived from the original PDF on January [commissioned June ]. Archived from the original on Capacity Factor, Intermittency, and what happens when the wind doesn't blow?
National Renewable Energy Laboratory. In intermittent production system, cost per unit may be higher because production is done on a small-scale. In continuous production system, cost per unit may be lower because production is done on large-scale.
In intermittent production system, wide ranges of products are manufactured. In continuous production system, normally one particular type of product is manufactured. In an intermittent production system, many detailed instructions must be provided depending upon the customer's specification. In continuous production system, single set of instructions is sufficient for operation. Here, there is no need to repeat the instructions. Intermittent production system requires staff with high technical skills and abilities.
Continuous production system requires more managerial skills and less technical skills. Storage of final products: In an intermittent production system, there is no need to store and stock the final products, because items are produced as per customer's orders. In a continuous production system, there is a need to store and stock the final products until they are demanded in the market.
In an intermittent production system, change in location is easy. In a continuous production system, change in location is difficult. In an Intermittent production system, capital invested is small.
In a continuous production system, capital invested is very huge.
A manufacturing method of producing several different products using the same production line. Once an initial production line has run, a second product will be produced which increases the amount of productivity a company is capable of at one time.
In continuous Production System, goods are produced on a large scale, so there are economies of large-scale production. Per unit cost: In intermittent production system, cost per unit may be higher because production is done on a small-scale.
Intermittent production system Intermittent means something that starts (initiates) and stops (halts) at irregular (unfixed) intervals (time gaps). In the intermittent production system, goods are produced based on customer's orders. Intermittent production is the common practice of using the same production line to produce different types of goods. The following are illustrative examples.
A intermittent production process a production process in which the production run is short and machines are changed frequently to make different products. Intermittent Production System According to E.S Buffa, intermittent production situations are those where the facilities must be flexible enough to handle a variety of products and sizes, or where the basic nature of the activity imposes change of important characteristics of the input (e.g., change in .