Renewables Integration and the Smart Substation
Written by Peter Vaessen
As we have heard time and time again, two key issues with our future energy systems are the integration of huge amounts of renewable energy sources into the grid, and the realization of active demand through customer involvement. These two issues combine to create the need for a smarter grid that can cope with generation and load with high coincidence factors without significant reinforcements.
Our future transmission system will likely be very similar to that of the present day, aside from the increase in power flows across the transmission network due to trading, and the additional presence of large-scale intermittent sources, such as (offshore) wind power plants and remote large scale photovoltaic systems. On the other hand, the local power distribution system(s) might be quite different from what we see today.
The future of the local power distribution system offers us (nearly) self-supporting rural, urban or industrial energy environments, compared with today’s more traditional (consumption only) behavior. A number of generators utilizing different technologies, based on renewable energy or combined heat and power, will be present at the distribution level. Furthermore, the future electricity customer will be more directly involved in the power system as he may own part of the assets at the local distribution level.
In this scenario, the goal of the future power grid operator is to achieve the best possible security for the network using the available facilities. This requires tools for assessing the vulnerability of the grid to possible contingencies, implementing protection and control that is responsive to the prevailing system conditions and minimizing the likelihood of blackouts resulting from various forms of instabilities and external threats. The goal is for the network to be adaptive and self-healing through quick and accurate assessment of the degree of damage and the pace of affected area expansion – reducing the effect of the disturbance by breaking it up and isolating it. The remaining parts of the network can then operate on a (slightly) degraded level. After the “storm,” the entire system can be restored again.
A crucial element of the future smart grid is the smart substation, and how this power and information exchange will be connected to the regional transmission and local distribution grid. The smart substation is, on one hand, the gateway to the many prosumers connected to the low voltage grid and, on the other, the connection to the higher voltage levels of the transmission grid and interconnectors.
DNOs are faced with an ever-increasing uncertainty for planning and operation. The size, location and timing of generation and load are often unpredictable. Investments in grid reinforcements may turn out to be uneconomic for the DNOs. This stimulates them to maximize the use of the existing network and to consider installing flexibility and intelligence in the grid instead of traditional grid reinforcements. Smart substations are capable of aggregating customer demand and supply. They can guarantee power quality, allow for controlled islanding, optionally store energy, and serve as an information and control gateway. This last part is possible through exchange agents between customers and the grid. And of course, smart substations are capable of physically facilitating the delivery of electric power.
An important question to consider in regard to the smart substation is how the power exchange layer will develop between existing large-scale generation – including, for example, offshore wind power – and the numerous distributed resources. Two scenarios are possible: the Camel scenario and the Dromedary scenario.
The Camel scenario envisages large power plants connected to one another via a high-voltage (HV) transmission network, while a low-voltage (LV) distribution network interconnects the micro grids that are (nearly) self-supported. Power is exchanged between the HV and LV layer over a relatively lightweight medium-voltage (MV) network. Alternatively, the Dromedary scenario assumes that both the large-scale plants and micro grids are connected to each other via a strong medium-voltage network.
If the Camel scenario becomes a reality, investments will be made mainly in the HV and LV network. When looking at the LV network, substantial investments would be made locally (probably at the customer site) to balance local supply and demand as much as possible, maintain voltage levels within tolerances, and control the power quality and reliability at the connection points. Because maintaining the voltage levels and control of the power quality is a difficult task in the LV network with a relative weak MV coupling, this, along with the function to allow controlled islanding, will probably be the main function of the intelligent node. Because the customer is largely involved, this model gives rise to public/private investment questions about who is responsible for what part and which costs, and who receives what benefits.
In the case that the Dromedary scenario becomes a reality, the MV network will be reinforced and serves as a strong primary means for keeping the voltage levels of the LV feeders within limits, and maintaining a certain level of power quality and reliability. This resembles most closely the present (ideal) network situation. Even in this strong MV network, maintaining the voltages within the tolerance band and assuring power quality and reliability with a number of small-scale, embedded generators will become increasingly difficult with direct control functionality only at the entrance point of the feeders. It is therefore likely that there will again be a demand for smart substations equipped with two-way communication and grid support functionality. The question that then arises is how the dispersed generators are controlled to offer grid support.
The conclusion here is that smart substations are an essential element for a reliable and sustainable power supply in the future and, depending on which scenario becomes a reality, will have a different function and a different realization path.
Industry movement with heat decarbonisation
It is estimated that the heat network market requires approximately £30 billion of investment by 2050 to meet the UK Government’s net zero targets, and the decarbonisation of heat has been highlighted as a particular challenge.
The Climate Change Committee’s Sixth Carbon Budget states the UK should target 20% of UK heat demand through low-carbon heat networks by 2050 - but as with most discussions surrounding mass decarbonisation, even reaching that target won't be an easy task. In the UK approximately 40% of energy consumption and 20% of GHG emissions are due to the heating and hot water supply for buildings.
The International Energy Agency (IEA) estimate that globally, around half of all energy consumption is used for providing heat, mainly for homes and industry.
Source: Heat Trust
This week saw some positive movement, however, with gas distribution company SGN and UK renewable energy solutions provider Vital Energi announcing a 50:50 joint venture, which will create an Energy Services Company (ESCO) representing utility infrastructure and heat network providers.
This includes delivery of heat to developments planned by SGN’s property arm, SGN Place, and the local vicinities where there is a demand for low-carbon heat.
The objective is to supply new and existing residential, industrial and commercial facilities and development activity is already underway for two projects in Scotland and the South East, with another 20 in the pipeline. SGN is looking to develop alternative heat solutions alongside its core gas distribution business and expand into the growing district heating market, recognising the future of heat is likely to include a mix of technological solutions and energy sources.
Vital Energi is seeking to expand into asset ownership opportunities to complement its core design, build and operations businesses. The complementary skillsets of both organisations will offer a compelling proposition for developers, commercial and industrial users and public sector bodies seeking low-carbon heat solutions.
SGN’s Director of Commercial Services and Investments Marcus Hunt said: “Heat networks are likely to play an increasing role in the delivery of UK heat in the context of net zero. The creation of this joint venture with market-leading Vital Energi enables us to build a presence in this emerging market, delivering new heat infrastructure and supporting decarbonisation.”
Nick Gosling, Chief Strategy Officer at Vital Energi, said: “Combining the resources, expertise and know-how of both organisations will allow us to play a major role in delivering the UK’s transition to low and zero-carbon heat.”
In March, the European Marine Energy Centre (EMEC) starting collaborating with Highlands and Islands Airports Limited (HIAL) to decarbonise heat and power at Kirkwall Airport through green hydrogen technology. 2G Energy was selected to deliver a CHP plant which generates heat and electricity from 100% hydrogen.
Heat decarbonisation options
The Energy & Climate Intelligence Unit (ECIU) highlights the following options for decarbonising heating.
Use renewable electricity to generate heat in the home. As power sector emissions fall, emissions associated with electric heating are decreasing rapidly.
Low carbon gases
Replace natural gas that most homes use for heating with hydrogen, which releases energy but not carbon dioxide, the only waste product is water. Biomethane is also an option as it produces less carbon than natural gas over a full lifecycle.
For hydrogen to work, the pipes in the national gas grid would need to be replaced and home boilers would need to be adapted or changed. This is possible but could incur considerable cost.
Biomethane is chemically identical to methane from natural gas, so is suited to existing infrastructure and appliances. It is unlikely, however, that it can be produced in sufficient quantities to replace fossil gas entirely.
A hybrid system combining both electrification and hydrogen is a third option. Here, heat pumps could be used to meet the majority of heat demand, with a (low carbon) gas boiler taking over in extremely cold weather. Advantages of this approach include helping establish a market for heat pumps while hydrogen is developed to displace natural gas in the hybrid system eventually, and the ability to call on hydrogen when heat demand is at its very highest.
Heat networks connect a central heat source to a number of buildings via a series of underground hot water pipes, and are popular in countries such as Denmark, where heat networks supply 63% of households. The Government expects the heat networks market in the UK to grow quickly to supply up to 20% of heat demand over the next decade or so, investing £320 million into its flagship Heat Networks Investment Project to help get this underway.
Heat networks work particularly well in built-up urban areas or industrial clusters where there is a large and concentrated demand for heat. Over time, it is thought that if the central heat source can be low carbon, then there is the opportunity to ensure that multiple homes and buildings are decarbonised at once.
Biomass can be used to reduce emissions when used instead of more polluting fuels like oil in off gas grid properties. Support for biomass boilers has been available since 2011 via the Renewable Heat Incentive (RHI), but take-up has been low.
Supply constraints also restrict the role that biomass – burning solid material such as wood – can play. In any case, according to the Committee on Climate Change, this resource may be better used in other sectors of the economy such as construction, where it provides carbon storage without the need for CCS and reduces demand for carbon-intensive materials such as steel and cement.
The Energy Transitions Commission (ETC)'s latest report sets out how rapidly increasing demand for bioresources could outstrip sustainable supply, undermining climate mitigation efforts and harming biodiversity, unless alternative zero-carbon options are rapidly scaled-up and use of bioresources carefully prioritised.
"Alternative zero-carbon solutions, such as clean electrification or hydrogen, must be developed rapidly to lessen the need for bio-based solutions," it states.
The overall decarbonisation of industry is another major challenge, especially among four sectors that contribute 45 percent of CO2 emissions: cement, steel, ammonia, and ethylene, according to a McKinsey report.
The process demands reimagining production processes from scratch and redesigning existing sites with costly rebuilds or retrofits. Furthermore, companies that adopt low-carbon production processes will see a short- to mid-term increase in cost, ultimately placing them at an economic disadvantage in a competitive global commodities market.
Ken Hunnisett is Project Director for the Heat Network Investment Project (HNIP)’s delivery partner Triple Point, which is the delivery partner for the government's Heat Network Investment Project, which is responsible for investing up to £320million in strategic, low-carbon heat network projects across England and Wales.
He is calling for the urgent need to invest in the development of new heating infrastructure to support the nation’s decarbonisation effort. So far £165m of HNIP funds have prompted £421m CAPEX, providing more green jobs as the UK economy eases from the lows sustained from the pandemic.
Decarbonising the UK's heating infrastructure is critical if we are to reach our net-zero goals and it’s crucial that progress is made in this decisive decade, he added.
"Heat networks are a part of the lowest-cost pathway to decarbonising our homes and workplaces in the future but are also the bit of the jigsaw that we can be putting into place now," he said. "Penetration into the UK market is still low, despite heat representing 37% of UK greenhouse gas emissions, the largest single contributor by some way. Funding needs to be urgently directed towards reducing the environmental impact of the residential sector, particularly given the slow pace of the decline in residential emissions in comparison to those of business and transport."
Currently, just 3% of UK buildings are serviced by heat networks. "Further investment in this industry, using public and private funds, will not only drive wider sustainability targets but will boost the economy by providing more green jobs as the country emerges from the pandemic," he said.