Grid Integration Of Renewables – Analysis
Variable solar and wind power differs from traditional power sources like coal, natural gas, or hydropower in important ways. The latter can produce power on demand, but solar and wind power are intermittent because the sun does not always shine and the wind does not always blow. Likewise, wave energy converters (WECs) are at an earlier stage of development than wind and solar power plants.
A variety of concepts have been proposed and tested worldwide, but only a few WECs have exported power to electrical grids. Therefore, the actual impact of integrating high levels of wave power into grids is still uncertain. When only a few power plants produce variable energy and their contribution to the overall power supply is low, grid operators can manage variability in the grid without much difficulty. To foster sustainable, low-emission development, many countries are establishing ambitious renewable energy targets for their electricity supply. Because solar and wind tend to be more variable and uncertain than conventional sources, meeting these targets will involve changes to power system planning and operations. Grid integration is the practice of developing efficient ways to deliver variable renewable energy (VRE) to the grid. Good integration methods maximize the cost-effectiveness of incorporating VRE into the power system while maintaining or increasing system stability and reliability.
Grid integration of renewable energy means reimagining operation and planning for a reliable, cost-effective, and efficient electricity system with cleaner new energy generators. This includes where it is built, how it is optimized, and how it is used to power a carbon-free future. It means providing grid operators with the situational awareness and control capabilities they need to plan and manage a rapidly changing energy resource mix.
The path forward involves assessing long-range demands and evaluating pathways for efficient performance. For example, projecting atmospheric patterns can help guide—and maximize—the sitting of solar or wind power. It also includes evaluating, scheduling, and optimizing future energy market design using advanced modelling and simulation to understand the operational connections to renewable energy availability, generator performance, grid reliability, and electricity delivery to customers.
Grid integration of renewable energy includes building resilience against threats, such as natural disasters and cyber threats. It also involves overcoming challenges, such as instantaneous to seasonal unavailability of renewable resources. By developing solutions and mitigative measures across both information technology and operational technology systems, we can prepare for a cleaner, greener, and more resilient energy landscape.
Grid integration is the process of incorporating new generations into an existing power system. The process involves understanding complex power grids and how they balance electricity supply and demand, along with evaluating how the integration of variable renewable energy will impact those grids.
Solar Panels and Wind Turbines Contribution to RE Production
Solar panels: Solar panels, or photovoltaic (PV) cells, convert sunlight directly into electricity. When sunlight hits the panels, it excites electrons in the cell, creating an electric current. This electricity can then be used immediately or stored for later use. With advancements in solar technology and decreasing costs, solar energy has become a significant contributor to the global energy mix.
Wind turbines: Wind turbines harness the kinetic energy of moving air to generate electricity. As wind flows over the blades of a turbine, it causes them to lift and rotate. This rotation drives a generator, which then produces electricity. Wind energy, especially offshore wind farms, has seen substantial growth in recent years due to its efficiency and decreasing installation costs.
Importance of Integration
The integration of renewable energy into power grids is paramount for several reasons. Firstly, traditional power generation methods, primarily reliant on fossil fuels like coal and natural gas, release significant amounts of carbon dioxide and other greenhouse gases. These emissions are primary contributors to global warming. By integrating renewable energy sources, we can significantly reduce these emissions and hence, slow down the pace of climate change. Secondly, renewable energy sources, such as solar and wind, are inexhaustible. Unlike finite fossil fuels, renewable sources ensure a sustainable energy future that helps reduce our dependency on depleting resources.
Burning fossil fuels releases pollutants that can harm public health and the environment. Transitioning to cleaner energy sources can reduce the incidence of respiratory ailments, cardiovascular problems, and other health issues linked to pollution.
Technical Challenges of Integrating
Natural gas and other fossil fuels have been the backbone of power generation for decades. However, their contribution to greenhouse gas emissions has expedited the shift towards renewable energy sources. In recent years, the shift toward renewable energy technologies has been monumental. With the adverse effects of climate change becoming more evident, the urgency to reduce carbon emissions and embrace cleaner energy sources has never been higher. Solar panels and wind turbines have become synonymous with renewable energy production. Also, solar energy, harnessed through solar power systems, and wind energy, captured by wind turbines, are leading the charge in the fight against climate change. Variable renewable energy (VRE), e.g. wave, wind and solar photovoltaic (PV) energy are highly dependent on weather conditions, daily cycles and seasonal patterns. Therefore, exporting large amounts of VRE to electrical grids increases the uncertainty and variability of the power output. Due to its fluctuating nature, VRE is more challenging when it comes to adjusting power output to changes in electrical demand.
Renewable sources like solar and wind are intermittent, meaning they don’t produce energy all the time. This unpredictability can make it challenging for grid operators to balance supply and demand. Many existing power grids were designed long before renewable energy became a viable option. Integrating these new energy sources often requires significant upgrades to the existing grid infrastructure. Due to the variable nature of renewable energy, there’s a need for efficient energy storage solutions to ensure power availability even when the sun isn’t shining or the wind isn’t blowing. Renewable energy sources can introduce fluctuations in the grid’s frequency and voltage, which can affect the stability and reliability of the power supply.
The transition from fossil fuels to renewable energy sources is not just a trend; it’s a necessity. As the world grapples with the dire consequences of climate change, the problem of how to integrate renewable energy into existing power grids has become a focal point for grid operators and energy enthusiasts alike. Integration of renewable energy into existing power grids and infrastructure is no small feat. The distributed nature of these energy resources, like solar systems and wind energy, means they are often dependent on weather conditions. This variability can pose challenges for grid stability. With renewable energy production often peaking during certain hours, energy storage technologies play an important role in ensuring a consistent power supply. However, significant investments are required to develop advanced technologies that can store energy efficiently. Grid operators are tasked with ensuring grid stability, especially with the influx of renewable sources. The integration of solar panels, wind turbines, and other renewable energy technologies can sometimes disrupt traditional grid operations.
In contrast to hydropower plants with large reservoirs, the primary energy source for wind, wave and solar power cannot be stored on-site for conveniently increasing power production at the request of grid operators. Low demand can be met by limiting generation, but increased demand can only be met if the VRE has available reserve power.
In addition, VRE plants are commonly connected to the grid using power electronic interfaces, which makes the operation of the generator independent of the voltage and frequency of the power grid. This allows wind turbines and WECs to operate at variable speeds for maximum power tracking and survivability in different weather conditions. However, this type of grid connection does not add rotational inertia to the power system.
Rotational inertia is the tendency of a spinning object to remain in motion. In power systems, it represents the kinetic energy stored in large rotating generators that keeps them running for a while, even when there is a sudden loss of power. It resists changes in the electrical frequency, giving the system time to respond and rebalance power supply and consumption. Due to the reduction in inertia, grids with high levels of VRE are vulnerable to large frequency deviations, which affect system stability.
Addressing Challenges
Traditionally, active power balance was provided by conventional generation, e.g. large hydropower and fossil-fuel power plants, due to their rotational inertia and ability to adjust the power output to meet changes in demand. In contrast, wind power plants mainly maximised their power output and exported power to grids whenever it was available. Due to the increasing levels of VRE and the replacement of fossil-fuel power plants, grid operators are now:
Defining more strict requirements for the interconnection: Some power systems now require that wind power plants provide frequency control support, depending on their rated power. Therefore, wind turbines do not extract maximum power from wind. Instead, they operate at reduced power, which enables them to increase and decrease their power output during specific frequency deviations.
Developing new services for faster frequency support: In case of major disturbances in the power system, generating units (e.g. wind turbines) providing the service must deliver power faster than in traditional frequency control. The power electronics interface can be controlled to emulate the inertia of synchronous generators or a constant power can be injected during a few seconds. In either case, a power reserve must be available.
To foster sustainable, low-emission development, many countries are establishing ambitious renewable energy targets for their electricity supply. Because solar and wind tend to be more variable and uncertain than conventional sources, meeting these targets will involve changes to power system planning and operations. Grid integration is the practice of developing efficient ways to deliver variable renewable energy (VRE) to the grid. Good integration methods maximize the cost-effectiveness of incorporating VRE into the power system while maintaining or increasing system stability and reliability. When considering grid integration, policymakers, regulators, and system operators consider a variety of issues, which can be organized into four broad topics:
New Renewable Energy Generation: Power system planners can secure and sustain investment in new VRE generation by aligning targets and incentives with grid integration considerations. Long-term, aspirational renewable energy targets establish a vision that can drive innovation in the policies and system operations that support clean energy. Also critical are “grid-aware” incentives (e.g., rewarding wind and solar generators that incorporate technologies that contribute to grid stability), which both motivate investment in renewable energy and mitigate the negative impacts of integrating these resources into the grid. As planners consider scaling up VRE generation, the inherent variability of wind and solar resources complicates evaluations of whether a system with significant VRE has adequate supply to meet long-term electricity demand. A variety of approaches exist for estimating the capacity value of VRE, as well as techniques that enable utilities and power system operators to use wind and solar to reliably meet electricity demand.
Integrating distributed photovoltaic (PV) solar power results in unique benefits and challenges compared to the integration of utility-scale wind and solar power. Significant localized growth in PV can raise concerns such as voltage violations and reverse power flow in low-voltage distribution systems. However, various studies have shown that positive impacts (e.g., reduced line losses and avoided generation costs) can also result from distributed PV. Updating interconnection standards, procedures, and distribution planning methodologies to better reflect the characteristics of distributed PV can help realize these benefits and delay or even prevent the need for grid reinforcement.
New Transmission Scaling up VRE generation requires grid expansion and upgrades so that power systems can access high-quality solar and wind resources, which are often remote from existing transmission networks. A well-crafted combination of policies, rules, and procedures encourages investment in large-scale transmission expansion. These measures not only improve the utilization of VRE but also potentially defer the need for network refurbishment.
Increased System Flexibility: Accessing sources of operational flexibility becomes increasingly important in systems with significant grid-connected solar and wind energy. System operating procedures and market practices—especially the implementation of real-time forecasting, faster scheduling, and ancillary services—are often among the least-cost options for unlocking significant flexibility without significant investments in new physical infrastructure. Another important institutional flexibility option is operational coordination between balancing authority areas, which enables the sharing of resources through reserve sharing, coordinated scheduling, and/or consolidated operation. Other sources of flexibility include flexible conventional generation and transmission networks. Additionally, demand response and storage are emerging as tools for increasing flexibility at very high penetrations of VRE. Options for procuring flexibility vary based on the regulatory context. For vertically integrated utilities, contractual or policy mechanisms provide the primary basis for encouraging the uptake of flexibility measures. In contrast, partially or wholly restructured power markets motivate flexibility through incentives and market design mechanisms, such as sub-hourly dispatch, ancillary services markets, and price-responsive demand.
Planning for a High-Re Future: In any power system, planning activities include assessing long-range demand and evaluating options for expanding capacity and transmission. With the introduction of significant VRE generation, power system planning increasingly focuses on evaluating options for increasing flexibility across the power system. Grid integration studies help establish flexibility requirements and build confidence among investors and operators that the power system can be operated reliably at increased VRE levels. A grid integration study simulates the operation of the power system under various scenarios, identifies potential constraints to reliability, and evaluates the cost of actions to alleviate those constraints. Robust grid integration studies are based on significant stakeholder input, along with a broad set of foundational data. Although grid integration studies usually include production cost simulations to model unit commitment and economic dispatch, determining the system-wide costs of integrating solar and wind power is much more challenging. The full costs and value of VRE assets to the power system depend on dynamic and complex interactions among these generators and a system’s loads, reserves, thermal generators, and transmission networks. Grid integration studies illuminate the obstacles and opportunities that wind and solar integration could pose to a power system, helping to dispel grid integration myths and misperceptions that inhibit large-scale deployment. These studies also lay the foundation for prioritizing and sequencing grid integration investments.
Balancing the Power Grid
Operating a power system relies on continuously matching power supply with consumption. This is necessary to keep the electrical frequency of the grid within the range of normal operation, a fundamental measure of the system stability. The frequency drops when the electricity demand is greater than the supply and rises when the demand is lower. Acceptable deviations during normal operation and large faults are specified according to local grid codes, which are sets of national (or regional) specifications that define the requirements for connecting power plants and other facilities to an electrical grid. Throughout the day, the demand must be met according to different timescales:
From seconds to minutes, the power generation is regulated to maintain the grid frequency within the operational range in case of disturbances. Regulation is performed both automatically through frequency control and manually by grid operators.
From tens of minutes to hours, the generation must be slowly adjusted to follow the natural changes in demand. This consists of increasing or decreasing the generated power, which can involve turning on/off generating units in the power system.
Daily, scheduling (i.e. generation planning) is performed to match the energy and peak power of the day. This requires predicting load, generation output and availability.
Economic Implications: Integrating renewable energy into existing power grids is not just an environmental imperative but also an economic one. The renewable energy sector, especially solar and wind, has been a significant source of job creation in recent years. From manufacturing to installation and maintenance, the industry offers a wide range of employment opportunities. Relying on renewable energy reduces dependency on energy imports, ensuring a more stable and predictable energy supply. This is particularly crucial for countries that heavily rely on energy imports, as it can significantly reduce their trade deficits. In many regions, renewable energy, especially wind and solar, has become the cheapest source of new electricity generation. As technology advances and economies of scale come into play. The cost of renewable energy is expected to continue dropping, leading to further savings for consumers.
Role of Education: As the world grapples with the challenges of integrating renewable energy, the role of education becomes paramount. An educated populace can make informed decisions, be it in their energy consumption habits or in supporting policies that promote renewable energy. With proper education and training, the next generation can lead the way in developing innovative solutions to the challenges faced in renewable energy integration. As the renewable energy sector grows, there’s a need for skilled professionals in various capacities, from research and development to installation and maintenance. Educational institutions play a crucial role in training this workforce.
Community Participation: The challenges of how to integrate renewable energy into existing power grids are significant, but they are not insurmountable. The final push requires collective action: Governments worldwide need to prioritize renewable energy, providing the necessary policy frameworks, incentives, and infrastructure. Businesses, big and small, have a role to play, be it through direct investments in renewable energy, adopting sustainable practices, or supporting research and innovation. Grassroots movements, community-led initiatives, and public awareness campaigns can drive change at the local level, making the transition to renewable energy a shared goal.
Role of Start-Ups: Start-ups are at the forefront of innovation in the renewable energy sector, bringing fresh perspectives and agile solutions. Many start-ups are developing cutting-edge technologies, from advanced battery storage solutions to efficient solar panel designs, pushing the boundaries of what’s possible in renewable energy. Several start-ups focus on micro grid solutions, allowing remote areas and individual communities to generate, store, and distribute their energy, reducing dependency on large-scale grids.
With the rise of digital technology, start-ups are creating platforms for peer-to-peer energy trading, predictive maintenance of renewable energy installations, and real-time monitoring of energy consumption and generation. Recognizing the financial challenges of renewable energy projects, start-ups are introducing innovative financing and business models, making it easier for consumers and businesses to adopt renewable energy solutions.
Future Technological Advancements
The future holds a plethora of technological advancements that will facilitate the integration of renewable energy:
Next-gen batteries: Advancements in battery technology, such as solid-state batteries, will offer higher energy densities and longer life spans, making energy storage more efficient.
Grid-interactive buildings: Buildings in the future will not just consume energy but also produce and store it, interacting with the grid in real time to optimize energy usage.
AI-powered grid management: Artificial Intelligence will play a pivotal role in predicting energy demand, optimizing distribution, and ensuring grid stability.
Wireless energy transfer: While still in its nascent stages, the concept of transferring energy wirelessly could revolutionize how energy is distributed and consumed.
Grid Integration Terminology
Balancing area: the collection of generation, transmission, and loads within the metered boundaries of the responsible entity (i.e., the balancing authority) that maintains a balance between electricity supply and demand within this boundary.
Capacity value: the contribution of a power plant to reliably meet demand, measured either in terms of physical capacity (kW, MW, or GW) or as a fraction of the power plant’s nameplate capacity (%).
Flexibility: the ability of a power system to respond to changes in electricity demand and supply.
Demand response: voluntary (and compensated) load reduction used as a system reliability resource.
Grid integration of renewable energy: the practice of power system planning, interconnection, and operation that enables efficient and cost-effective use of renewable energy while maintaining the stability and reliability of electricity delivery.
Grid integration study: an analysis of a set of scenarios and sensitivities that seeks to inform the stakeholders on the ability and needs of a power system to accommodate significant VRE.
Storage: technologies capable of storing electricity generated at one time and for use at a later time.
Variable renewable energy (VRE): electricity generation technologies whose primary energy source varies over time and cannot easily be stored. VRE sources include solar, wind, ocean, and some hydropower generation technologies.
Variability: the changes in power demand and/or the output of a generator due to underlying fluctuations in resource or load.
Uncertainty: the inability to perfectly predict electricity demand and/or generator output.
