Generally, anything that uses power is an electric load, with its usage measured in watts. As loads are a measure of power, they determine how much electricity is required to operate an appliance or asset.
Different types of electrical loads
When looking at the definition of load in electricity, there is a difference between domestic loads and power system loads.
Domestic load
A domestic load is the energy that is consumed by domestic or household appliances, such as televisions, toasters, kettles, hair dryers or similar appliances.. As every household has different assets installed or plugged in, the domestic load varies from household to household. To understand the difference between the three, it is important to know that voltage (measured in volts) refers to the amount of potential energy between two points on a circuit, while current (measured in amps) is the rate at which the charge flows past a point in the circuit.
Within a household, there are three main types of domestic electrical loads:
- Resistive loads: Any electrical load that consists of a heating element, such as lamps, ovens, toasters or space heaters. Current and voltage patterns are in sync.
- Inductive loads: Uses wire coils to store magnetic energy and create an inductive field so that the current wave lags behind the voltage wave. Examples here are dishwashers, washing machines, refrigerators or air conditioners.
- Capacitive loads: Provides the largest power factors and are often used to boost electrical circuits. They are only used to support other electrical loads, such as inductive loads. Here, the current peaks before the voltage does.
Power system loads
The power system loads can be further divided into different categories depending on how they contribute to the overall electricity demand. This division is helpful, as they help to analyze and manage the energy distribution efficiently. Power system loads are categorized the following way:
Gross load
The gross load is the total amount of energy that is required to serve demand for a country or region throughout the day. A gross load peak is when the electricity required is at its highest level of the day, usually occurring in the late afternoon and aligned with the time that consumers’ demand for energy increases. As part of power system loads, the gross load determines the total electricity demand that must be met by all energy sources.
Residual load/net load
Residual load, also referred to as ‘net load’, is the gross load minus electricity generated by variable renewable energy (VRE), such as solar or wind. It essentially shows how much demand is left for conventional power plants to operate. Thus, residual/net load accounts for the portion of power system loads that are not covered by renewables
Gross load and net load in Europe in July 2023
As the annual efficiency ratio (AER) capacity increases, the net load decreases and can even become negative. Thus, it can be broken down into a positive and a negative residual load.
Positive residual load
The positive residual load describes a situation in which renewable energy resources such as wind or solar do not produce enough energy to meet demand. This means the residual load is positive. When this happens, conventional energy sources (mostly high-emission ones) must cover the remaining electricity demand that renewables cannot supply. Currently, residual load is largely met by conventional sources. Luckily, as storage solutions and alternative renewable sources advance, the reliance on fossil fuels can be reduced.
Negative residual load
A negative residual load occurs when variable renewable energy not only covers all electricity demand but also provides a surplus of energy. As renewable energy capacity is still growing, negative residual load is currently rare. It is most common in countries with a high solar power capacity, such as in Germany and Spain, and typically takes place during the middle of the day when solar energy peaks, as seen below on three occasions in July 2023.
In this case, the excess electricity must either be stored, converted for later use or transported to regions where demand is higher. The challenge, however, is that sunshine and wind are not evenly distributed across a country, so energy transportation and grid balancing are crucial. Grid stability issues can arise when there is too much excess energy without sufficient storage or export capacity, requiring interventions such as curtailment of renewable generation to avoid imbalances.
In this case, the excess electricity must either be stored, converted for later use or transported to regions where demand is higher. The challenge, however, is that sunshine and wind are not evenly distributed across a country, so energy transportation and grid balancing are crucial. Grid stability issues can arise when there is too much excess energy without sufficient storage or export capacity, requiring interventions such as curtailment of renewable generation to avoid imbalances.
Positive and negative residual load in Germany in July 2023
Understanding these different types of loads is essential for analyzing energy consumption patterns, which are captured in load profiles. These load profiles help visualize how different appliances and systems consume electricity over time, aiding in optimization and cost reduction.
Electrical loads in comparison
Different appliances consume different amounts of electricity. The following list shows common household appliances and their maximum power consumption per hour of use:
Electrification and rising electrical loads
As we can see above, heat pumps and electric vehicles – two of the most common electricity-consuming distributed energy resources (DERs) – require a large amount of electrical energy to function. However, unlike electric stoves or electric boilers, they are flexible assets, which means their electricity flows can be monitored and their usage controlled. When integrated into an energy management system, heat pumps, which provide both heating and cooling, and EVs can be used at optimal times, so that their consumption period is shifted to minimize costs. They can even be used to store energy with bidirectional charging and thermal energy storage. This not only ‘relieves’ the grid during peak electricity demand periods,it also allows them to store surplus energy and feed it back into the grid if energy supply is low.
Integrating electricity, heating and mobility in this manner is part of a wider trend called sector coupling, which enhances the efficiency and sustainability of energy systems by creating synergies. Adding an increasing number of loads into energy systems, while at the same time as increasing variable renewable energy sources, can be overwhelming and hard to balance. With holistic smart energy solutions, however, flexible loads can enhance grid stability and present valuable opportunities.
As more and more households and businesses integrate electricity-intensive systems such as electric vehicles and heat pumps, load profiles are becoming increasingly important. By analyzing these profiles, consumers can optimize when and how they consume energy to reduce peak demand and improve efficiency.
Load management strategies
Electricity supply and demand loads are often misaligned. For example, consumers often use the most energy in the early evening when the sun is no longer shining. But with the right load management strategy, consumers can adapt to these fluctuations and utilize the full potential of their power-generating and -consuming assets to minimize their electricity bill. Load management describes the active control of electricity consumption. Depending on your setup and connected assets, there are several ways to manage loads. Effective load management strategies are closely aligned with load profiles as they utilize real-time and historical energy consumption data to optimize energy usage. Let’s take a look at some strategies:
Peak shaving
Peak shaving reduces the demand for electricity at peak load times in order to avoid grid loads and reduce costs. As part of load management, it increases energy flexibility by shifting or reducing consumption, ensuring stability and supporting the integration of renewable energies.
Dynamic load management
Dynamic load management optimizes energy usage at sites with multiple charge points by monitoring the grid connection load in real time and adjusting power distribution to each charge point, ensuring capacity limits are never exceeded.
Demand-side flexibility
Demand-side flexibility, also known as demand-side management (DSM), includes policies, strategies and technologies that aim to reduce electricity consumption during peak demand periods, often through financial incentives, load shifting or other measures. This flexibility is a key component of load management strategies aimed at optimizing energy use and ensuring a balanced grid.
What is a load profile?
A load profile is a visualization of your energy consumption on a daily or seasonal basis. It is usually illustrated by a rectangular graph that shows the current load profile and allows users to monitor changes in energy consumption and optimize their system. Depending on the customer type, the profile can vary between residential, commercial and industrial load profiles. They are frequently used in home energy management systems. The maximum demand over a billing period is calculated using a load time interval. To generate an accurate load profile, hourly measurement data is crucial.
How is a load profile calculated?
Load profiles are important tools because they provide insight into the consumption of energy devices as well as allow users to optimize their power usage. On top of that, they help determine the design capacity for system components like batteries or inverters. There are different approaches on how to create a load profile. Let’s take a look at two of them:
24-hour method
The 24-hour method, also referred to as the daily load profile, calculates the average power consumption over, as the name suggests, 24 hours. Time is controlled by ‘on’ and ‘off’ times, representing switching the load on and off. For load systems that are required continuously for 24 hours, the on time is displayed as 00:00 and off as 23:59. This method is often used in solar based systems because it helps to estimate how the energy demand and solar generation is matched throughout the day. Analyzing the daily fluctuations allows better planning of energy storage and efficient use of solar energy.
Autonomy method
The autonomy method focuses more on back-up systems, such as batteries, to ensure a reliable electricity supply even if the main power source is unavailable. It determines the average power demand over a specific backup period during which consumers rely entirely on stored energy. The autonomy method helps to determine the battery capacity that is needed to maintain the power supply without interruptions. This method is useful for off-grid systems or backup solutions in renewable energy setups.
Benefits of electrical load profiles
Load profiles are important in optimizing energy management systems because they provide detailed insights into electricity consumption patterns. By analyzing this, data companies can identify opportunities for reducing costs. If companies can adjust their consumption by predicting fluctuations in demand, they can reduce grid charges. One of the main benefits of load profiles is the demand forecasting which allows for an efficient allocation of resources so that the energy usage can be planned more effectively. It also provides quick insights into consumption deviations and helps to avoid interruptions.
Grid stability benefits largely from standard load profiles as they help to predict electricity demand and ensure a reliable supply. By analyzing load patterns, grid operators can foresee fluctuations and proactively take measures to balance supply and demand, reducing the risk of overloads or congestion. This predictive capability is particularly important for the integration of renewable energy sources, which can become unpredictable due to weather conditions. Without accurate load profiles and regular meter readings, grid operators face challenges in supply planning, which can lead to inefficiencies, unexpected outages and instability in the energy grid.
Load forecast
A load forecast is a prediction of the electricity that is needed at a given time and also includes how that demand influences the grid. It is important for the operational planning for power systems and helps to prevent outages while maintaining the overall grid stability. A load forecast can improve the efficiency of energy systems and supports demand-response that shifts the energy usage in order to manage peak-loads.
There are three different types of load forecasting that influence the decision on capacity extension, infrastructure development and maintenance.
Short term forecasting
A short-term forecast covers a period up to a week relying on day-ahead predictions. It includes weather data and recent load trends for real-time grid management and enables system operators to make momentary decisions on how much power to generate and where to direct it. It is important to forecast and predict accurately and data driven information, as even small errors can lead to energy waste and overloaded power lines.
Medium-term forecasting
Medium-term forecasts cover periods between a week up to a year. They are mainly used for maintenance scheduling. They take seasonal variations of electricity consumption into consideration as well as planned outages.
Long-term forecasting
A long-term forecast is more extensive than the other two and ranges from anything to over a year. It considers demographic changes, economic growth as well as potential changes in energy policy and its impacts. The focus of long-term forecasts is system planning and optimization. These forecasts support utilities in where to invest in new power generation capacity and balancing different sources of energy.
Extending the load profile
Extending load profiles is essential for optimizing energy management in smart grids, especially when integrating intermittent renewable energy sources. By adding renewable energy generation to load profiles, grid operators can anticipate fluctuations and adjust operations, for example, by activating energy storage or shifting demand to periods of high renewable energy. This extension also improves energy efficiency by identifying opportunities to reduce consumption during peak demand periods when less renewable energy is available, which can be combined with demand reduction strategies. Flexible solutions such as dynamic tariffs allow consumers to optimize their consumption based on real-time price signals, which in turn supports load balancing, peak shaving and grid stability. Integrating these solutions into energy management systems increases forecasting accuracy, streamlines energy distribution and improves the overall resilience and efficiency of the grid.
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