Integration of renewables into the grid

As renewables approach 50% of global electricity generation, issues related to storage and grid integration are becoming more important than the price in policy-making.

Myths and Solutions for Renewables in the Grid

There are many incorrect assumptions still prevalent, which are no longer so correct in theory and practice. Here are some of those incorrect presumptions:

Renewables such as wind and solar can never replace the conventional power stations’ role as provider of the baseload.

Examples of Denmark, Germany, and Australia have shown that periods of 100% renewable power supply is possible and practical, without destablising the grid. The previous system of large, centralized production from nuclear and fossil generating plants is progressively being replaced by a more efficient, decentralized system. Variable (or intermittent) solar and wind can be balanced with elements such as flexibility of supply (on-demand) and storage. Technologies enabling load management, to spread load demands, smart grids, to encourage rational use, such as timing of appliance use and charging of batteries and electric vehicles, with power availability and price incentives, will allow renewables to comprise the ‘baseload’.

Conventional power (hydro, fossil, nuclear, and biomass) is relegagted to the role of despatchable power. This is the power that can be shut down or powered up quickly when needed, to meet the peak times when intermittency limits supply.

Wind and solar are intermittent and unpredictable

Wind and solar can be predicted with a high degree of predictability. A smart system can then regulate demand, also with price incentives, to adjust demand to avoid shortfalls.

Storage is essential for renewable energy systems to work, but inefficient and expensive

Storage options are many: hydrogen, batteries, thermal salts, and pumped hydroelectric, to name but a few. Storage helps balance out supply and demand. However, more important for renewable power integration and power supply reliability is the adjustment of the grid to greater flexibility and management, pan-regional grid interconnections, and despatchable power sources (e.g. CHP, combined heat and power).

The greater the percentage of renewables the greater the risk of grid instability and black-outs

This fear is being proven unfounded as smart systems become more ubiqitous, allowing a smoother integration and control of variable electricity supplies. In practice, grid operators are experiencing an increase in grid supply reliability as the percentage of renewables increases. The average blackout time in Germany has fallen by 50% in regions with 40% renewable energy supply.

Renewables need an equal amount of fossil fuel capacity in the background, offsetting the carbon emissions benefits

Quite the opposite is the actual experience. Renewable energy and storage in combination with grid-management improvements leads to the elimination of ‘background’ fossil fuel stations, so-called ‘spinning reserves’. In other words, good management and flexibility eliminates wastage, represented by fossil fuel. Examples of grids which have achieved 100% renewable energy without spinning reserves include Uruguay, Costa Rica and Tasmania.

The duck curve, a late afternoon load spike coinciding with the fall in solar generation

The curve can be levelled out with short-term balancing and storage (especially electric vehicles). Tools include ‘time-of-day’ pricing, which smooth out the demand curve.

Excess renewable power will be wasted, raising retail prices of electricity

Excess power can be used in many systems, such as power-to-heat, pumped hydro storage, hydrogen, and synthetic fuel generation.

Renewable energy needs to be transported large distances, and this is inefficient and expensive

There is much potential in local use of renewable energy, especially solar on roof-tops. This decentalization reduces the reliance on long-distance power transmission. New HVDC transmissions lines are more efficient than previous AC lines, and will enable continent-wide sharing, increasing efficiency and stability of networks.