Demand flexibility: How load shifting helps in the dark doldrums
Supply is not the only decisive factor in meeting the demand for electricity during dark doldrums. Reducing the demand for electricity itself can also reduce the residual load.
Reduce residual load with flexible demand
Electricity generation and consumption must always be physically Balance stand. Up to now, power plant output has mainly been adjusted to consumption, i.e. the production side has been influenced. In future, the Role of flexible demand more relevant, which is largely automatic thanks to digitalisation and energy markets. Demand flexibility is often also referred to as load shifting or demand response. These terms mean that power consumption is not fixed, but moves over time can become. In a dark doldrums, i.e. a phase with little wind and little sunshine, the so-called "solar radiation" increases. Residual load (uncovered residual electricity demand). This refers to the proportion of electricity consumption that is not covered by renewable energies such as solar and wind and therefore has to be offset by storage, imports or conventional power plants.
The higher the residual load, the greater the Controllable capacities step in. Electricity generation is then more expensive and the electricity price is often higher. Very flexible consumers will avoid such time windows of their own accord anyway. If many flexible consumers pause or throttle back briefly during precisely these hours, these load peaks decrease. This means we need fewer residual load power plants and directly reduce the cost and risk peaks in the system.
The decisive factor here is that the aim is not to reduce overall consumption, but to the shift to time windows with high renewable electricity generation and low demand. (e.g. in phases with a lot of wind and sun. There is a surplus of electricity, so prices fall. There are different types of load shifting depending on the duration.
Short-term load shifting
It is important to know that electricity consumption does not simply ‚fail to materialise‘. The Consumption then takes place sooner or later This takes place at times when the residual load is lower, the system is more relaxed and there is a tendency for the Electricity cheaper is.
This can mean during a dark doldrums: We avoid the most expensive two to three hours in the early evening and shift consumption to a night or morning window, in which the load is lower overall. This smoothes the residual load curve, reduces price peaks and relieves critical grid elements. This is short-term load shifting. You utilises existing buffers in processes - e.g. thermal storage (pre-cooled cold stores, pre-heated buildings), production buffers (temporary storage) or electrical storage in the broadest sense (batteries in vehicle fleets). This type of load shifting is called largely automatic controlled by energy prices that are known for every quarter of an hour of the following day.
Food cold chains
Pre-cooling supermarkets, storage rooms and large warehouses Refrigeration systems (e.g. at night/early in the morning) make it possible to reduce consumption for a few hours during price peaks and still keep temperatures within the permissible range.
Building technology and heat pumps
These flexible consumption devices will be able to postpone large amounts of energy. For example, a consumer can postpone the charging of an electric car from 7 p.m. to 3 a.m. if the next journey is not planned until 8 a.m. the following morning. The vehicle's energy management system or app takes over the control. Heat pumps also generate heat outside the residual load peaks. The heat that is then generated is fed into heat storage units that provide heat during residual load peaks.
Industrial ovens and electric boilers
The aluminium, steel, chemical, glass and ceramics industries have many large-scale consumers, many of which can be flexibilised. A very well-known example is TRIMET Aluminium in Germany with the „Virtual battery“: The smelting furnaces for aluminium production (electrolysis cells) are operated in such a way that they can temporarily modulate their electrical output up or down by a noticeable amount without jeopardising product quality. Output is reduced during lulls or price peaks and increased during favourable hours. In this way, TRIMET provides flexible load for the market (including balancing power) and helps to smooth out residual load peaks.
Preheating processes and power-to-heat in district heating
In district heating, temperature buffers can be utilised and pre-charged if necessary. Power-to-heat systems (e.g. electric heaters) can briefly reduce their electrical output during peaks.
Compressed air systems
Compressors in production plants generate a „reserve“ at times when the residual load is low. This means that they only have to run on minimally during high-load windows.
Water/waste water
Elevated tanks of municipal utilities can be filled to a greater extent before shortages on the electricity market. During the residual load peaks, the filled reservoir is then utilised without having to be pumped up. Sewage treatment plants can also postpone energy-intensive aeration phases.
Data centres - shifting non-urgent workloads
Certain computing processes such as caching, ETL pipelines, backups and model retraining can be postponed or staggered. Data centres can also use short-term throttling during price peaks (reduce clock rates). These computing processes can be relocated internationally or made up for when electricity is not in short supply.
Paper/cement mills
Mill operation is distributed over the shift and reduced during peak time windows. Intermediate storage buffers the material flow.
Long-term load shifting
The next stage is longer-term load shifting: some electricity consumption can be reduced by 12, 24 or even 48 hours be pushed. This is particularly Valuable for shorter periods of darkness or at the end of a dark doldrums. Here, too, it is the Energy markets and forecasts in energy marketing, which control load shifting or provide the signals to adjust production processes or workflows because this can save costs.
When the wind picks up again, stock market prices fall and renewable electricity is available in abundance again, these shifted loads will be specifically made up for or, in some cases, specifically brought forward. Such flexible loads include electrolysers for hydrogen production, large-scale heat storage in district heating, some data centres and non-urgent industrial batch processes. Within certain limits, the depots of large e-bus and logistics fleets are also flexible for several days, e.g. at weekends. Result: We consume more electricity precisely then, when the supply is large and favourable again, and less electricity precisely when there is a shortage in the system. This helps Demand flexibility very practical to get through a dark doldrums safely.
Electrolysis/H₂ production
For cost reasons, hydrogen is generally produced during periods of high renewable electricity production. Largely throttle back during the lull; postpone production to windy days after the lull („H₂-follow wind“).
District heating with large storage tanks
Charging phases of heat storage tanks (hot water/steel storage tanks) can be planned specifically before and after the lull. During the doldrums, storage tanks are discharged and electrical heat generators are minimised. Large heat pumps can then be started up during periods of low load in the dark doldrums.
Industrial batch processes (chemicals, pharmaceuticals, food)
Non-time-critical batch production can be postponed by 12-72 hours as planned. Non-time-critical, energy-intensive cleaning and sterilisation processes take place after dark periods.
Construction and material drying
Electric drying and heating canons in the schedule could be staggered so that energy peaks are avoided and the main load falls on windy days.
Agricultural consumption
In particular, the aeration, drying or milling of grain, as well as the switching times of irrigation pumps, cold stores, etc. can be postponed.
Data centres - HPC/Rendering
Time-uncritical AI training/simulation jobs or renderings could be deliberately put on the back burner.
Long-term heat storage
The long-term heat storage units are heated during periods of peak solar irradiation (summer and autumn) and during wind peaks during storms and release the heat during dark doldrums. Electricity for heat generation can then be saved during the dark doldrums.
Pumping operation for mine dewatering
Groundwater lowering or mine water management can be controlled based on prices and forecasts. Before the dark doldrums, the water level is lowered in a targeted manner using variable-speed pumps in order to build up a water level reserve. During expensive slack periods, the pumping of mine water or the lowering of groundwater is reduced within the authorisation limits and made up for later in favourable time windows.
„Demand-side flexibility is a game changer for the energy system. It is the key to ending global dependence on fossil fuels.“
Fuel switch is not a time load shift, but is nevertheless important and should therefore be mentioned here. With the fuel switch fuel is changed in times of scarcity with high electricity costs. For example, process heat is then generated by gas or wood instead of electricity during periods of darkness, if their prices are more favourable. Of course, this only works in systems that fulfil the technical requirements.
Safely through the dark doldrums: the two-page guide
The fact paper "Dark doldrums" shows on two pages how dark doldrums can be overcome today, tomorrow and the day after tomorrow. Which fuels will we use? Which technologies will be used? How will battery storage help? How will biogas develop over the next few years? We have summarised the most important points on this website for you.