The share of renewables in overall power generation is rapidly increasing, both in developed and developing countries. Furthermore, many countries have ambitious targets to transform their power sector towards renewables. To achieve these objectives, the structure and operation of existing power grid infrastructures will need to be revisited as the share of renewable power generation increases.
Renewable energy technologies can be divided into two categories: dispatchable (i.e. biomass, concentrated solar power with storage, geothermal power and hydro) and non-dispatchable, also known as Variable Renewable Energy or VRE (i.e. ocean power, solar photovoltaics and wind). VRE has four characteristics that require specific measures to integrate these technologies into current power systems: 1) variability due to the temporal availability of resources; 2) uncertainty due to unexpected changes in resource availability; 3) location-specific properties due to the geographical availability of resources; and 4) low marginal costs since the resources are freely available.
A transition towards high shares of VRE requires a re-thinking of the design, operation and planning of future power systems from a technical and economic point of view. In such a system, supply and demand will be matched in a much more concerted and flexible way. From a technical perspective, VRE generation can be ideally combined with smart grid technologies, energy storage and more flexible generation technologies. From an economic perspective, the regulatory framework will need to be adjusted to account for the cost structure of VRE integration, to allow for new services and revenue channels, and to support new business models.
There are several technological options that can help to integrate VRE into the power system grid: system-friendly VREs, flexible generation, grid extension, smart grid technologies, and storage technologies. New advances in wind and solar PV technologies allow them to be used over a wider range of conditions and provide ancillary services like frequency and voltage control. Flexible generation requires changes in the energy mix to optimise production from both dispatchable and non-dispatchable resources. Smart grid technologies can act as an enabler for VRE integration, given their ability to reduce the variability in the system by allowing the integration of renewables into diverse electricity resources, including load control (e.g. Demand Side Management (DSM), Advanced Metering Infrastructure (AMI), and enhancing the grid operation and therefore helping to efficiently manage the system’s variability by implementing advanced technologies (e.g. smart inverters, Phasor Measurement Unit (PMU) and Fault Ride Through (FRT) capabilities).
Energy storage technologies can alleviate short-term variability (up to 2 Renewable Energy Integration in Power Grids | Technology Brief several hours), or longer-term variability through pumped-storage hydroelectricity, thermal energy storage or the conversion of electricity into hydrogen or gas.
Two immediate applications for deploying innovative technologies and operation modes for VRE integration are mini-grids and island systems. The high costs for power generation in these markets make VREs and grid integration technologies economically attractive since they can simultaneously improve the reliability, efficiency and performance of these power systems. This is, for example, the case of the Smart Grid demonstration project in Jeju Island, South Korea.
Furthermore, the right assessment and understanding of VRE integration costs are relevant for policy making and system planning. Any economic analysis of the transition towards renewables-based power systems should, therefore, consider all different cost components for VRE grid integration, such as grid costs (e.g. expansion and upgrading), capacity costs and balancing costs. Integration costs are due not only to the specific characteristics of VRE technologies but also to the power system and its adaptability to greater variability. Therefore, these costs should be carefully interpreted and not entirely attributed to VRE, especially when the system is not flexible enough to deal with variability (i.e. in the short-term).
Moreover, RE integration delivers broader benefits beyond purely economic ones, such as social and environmental benefits. Even though not straightforward, these externalities should be considered and quantified in order to integrate them into the decision-making process and maximise socio-economic benefits.
Due to the rapid technological progress and multiple grid integration options available, policy makers should build a framework for RE grid integration based on the current characteristic of the system, developing technological opportunities and long-term impacts and targets. In particular, policy makers should adopt a long-term vision for their transition towards renewables and set regulatory frameworks and market designs to foster both RE development and management of greater system variability. Such regulatory frameworks could include new markets for ancillary services and price signals for RE power generators that incentivise the reduction of integration costs.
Source: IEA-ETSAP and IRENA