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Energy Storage and Demand Management

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Table of Contents

 Executive Summary

This report discusses renewable energy storage and management in Scotland. It consists of four major sections.

The first section presents the impacts of generating renewable energy upon demand management, hypothesized under three scenarios, each with different rates of capacity increases. Demand levels are met effectively under the three methods.

The second section is concerned about the consequences of either increasing or decreasing renewable energy generation within the Scottish transmission line. Increasing renewables generation would not only modify how the grid network operates but would also entail more financial burden for Scottish producers than for other producers because the former are farther from the centres of demand. A decreasing generation would technically increase the dependency on conventional resources and that it will not entail additional costs.

The third section explores the optimal combination of different renewable energy sources for Scotland. Although a national report says that there is not the right mix that would work best for the country, the combination of wind and marine power is recommended nevertheless.

Finally, the fourth section discusses the importance of energy storage for renewables. It further explores additional storage facilities that Scotland would need to accommodate future demand effectively.

This report concludes that fully realizing the potential of Scotland will make the country one of the largest sources of renewable energy, thereby affecting demand in the global scale.

Energy Storage and Demand Management 

Scenarios for Generating Renewable Energy: Impact on Demand Management

Background

Renewable energy is an effective potential alternative to moderating the effects of climate change. However, renewable energy sources only account for 19.6% of global electricity and 13.5% of global energy demand (IEA, 2004, cited in Neuhoff, n.d.). While they are indeed limitless and reduce costs of operations in energy generation, renewable sources produce an unreliable energy supply since the weather, on which renewables much depend, can become very unpredictable so that its generation may not come in consistently large quantities that meet demand. Generation of renewable energy relies on several technical, economic, and social and environmental factors (Kopacek & IFAC, 2006). 

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Much of the carbon emissions come from conventional electricity consumption and transportation. Still, renewable energy sources encourage harmless ecological exploitation because they do not give off hazardous byproducts (e.g. carbon dioxide) upon consumption. In the United Kingdom, Scotland generates 50% of the country’s renewable energy chiefly from wind, hydropower, marine and biomass sources (Great Britain House of Lords, 2008). Scotland has approximately 60 GW of raw renewable electricity sources that could make the country a world leader in renewable energy generation (Scotland, 2009). The government can generate renewable energy five times more than it consumes (McDermott, 2010). 

But the challenge remains, however on the transmission of this energy potential in which regulatory, financial, logistical, and environmental factors should be taken into account especially in improving the grid network and the policy considerations (Scotland, 2009). The Scottish government, in response to its commitment to reduce carbon emissions by at least 42% in 2020, aims to “flex generation [of electricity] to meet demand, and …flex demand to meet generation” (Scotland, 2010a). Taken from a national report, the following scenarios present how RE generation affect demand management in Scotland. In all three methods, demand levels are satisfied. In the second and third scenarios, supply will exceed demand with transmission upgrades, constraints approaches, and reduction of need in consideration.

Scenario 1

The Scottish government had recently increased its renewable target to 80% for 2020 due to the expansion in wind power through which renewables may be primarily deployed for the next nine years without the need of modifying the current systemic frameworks (Scotland, 2010a). This imposed increase will affect Scotland’s capacity to generate within the same period through a generation portfolio. In this scenario, positive power flows will be contained from 2020 to 2030. Additional power generated may be included in significant volumes through transmission upgrades between Scotland and England within the following time frames: 2015, 2020, and 2030. By 2020, 61% of the Scottish generation output is renewable, and by 2030, it will rise to 76%. The report implies that this will allow the country to hit the target. The report further indicates that Scottish generators will be able to produce from 12 GW to 17 GW within ten years from 2010 and approximately 18 GW by 2030 due to the increased generating capacity (Scotland, 2010a). Centralized energy storage will be less necessary, and location-specific constraints will only have to be addressed locally.

Scenario 2

 In this scenario, the targets are based on practical perceptions on renewable growths from which offshore wind sector contributes largely. More precisely, 12 GW of wind, 700 MW of marine and 400 MW of biomass installed in 2020 will drive the rise of generation capacity. It will reach 70% and 83% by 2020 and 2030 respectively. Mainly, this is an increase from 12 GW to 21.5 GW by 2020 of installed capacity. Therefore by 2030, there will be an overflowing supply of renewables even if thermal generation will be constrained (Scotland, 2010a). The percentage contribution of renewable energy to the final energy demand rise climb from the 2008 figure, 27% to 120% in 2020 and 58% in 2030 (Scotland, 2010a). By 2015, satisfying 50% of renewable electricity demand will be reached (Scotland, 2010a). 

Scenario 3

With increased capacity from 12 GW to 25.5 GW to 29 GW by 2020 and 2030 respectively, the percentage of renewable power as 73% by 2020 and 88% by 2030. Installation of 16 GW of wind mainly from offshore wind, 1 GW of marine and 400 MW of biomass capacity will drive the increased in total by 2020. Like under the second scenario, generating renewable energy will prevail in the locality, producing more renewables than it needs; and that by 2015, renewables will meet 50 per cent of the demand for electricity (Scotland, 2010a).

Consequences of Increasing and Reducing Renewable Generation within the Scottish Grid

Increasing RE Generation

Aside from wind power, hydropower, tidal, and wave power will gain broader importance. Scotland has an abundant amount of rainfall and 1.2 GW of wave and tidal energy being processed within ten plant sites (Warren, 2002; Great Britain House of Lords, 2008, p. 119). Hydroelectricity will be mainly used in coping with the increasing intermittence in that pumped-storage hydroelectricity will have to be installed to manage peak demand periods (Great Britain House of Lords, 2008, p. 120). Therefore, increasing renewable generation could change the way the Grid network operates. Branches of the system will have to be more responsive to change to handle the additional generation (Great Britain House of Commons, 2008). Scotland’s transmission line has to be upgraded; otherwise, the renewable potential will substantially diminish to 33 TWh, according to a Scottish Executive study in 2001 (RSPB, WWF, & FOE, 2006). 

Additionally, if intermittent renewables will be increased, then dependence on fossil fuels as a source of electricity will decrease. It will reduce the burning of fossil fuels. Usage of gas and oil will have to be reduced so that the demand for electricity from the heat and transport sectors will increase (Scotland, 2009).

Scotland has an unquestionable comparative advantage in terms of producing natural energy. Bringing in an increase of intermittent renewable generation into the Scottish grid would mean that Scotland will have to connect to the additional areas of demand. Scotland has produced renewable electricity more than it needs; therefore, they will have to provide outside the locality. The increase would technically increase supplies. The Scottish government invests on-grid reinforcement for cross-border transmissions. ScottishPower, an international energy transmission network, developed an £84 million grid reinforcement for a better cross-border massive renewable energy transmissions (New Energy Focus, 2008). It has increased Scotland’s export capacity from 2200MW to 2800MW two years after the reinforcement (New Energy Focus, 2008). 

There have been twice as much electricity generated by renewable sources from Scotland since 2000 (see Table 1) (Scotland, 2010b). This means that there has been a consistent increase of grid connections — transmission upgrades as investments. However, grid connections are already a costly enterprise. With Great Britain’s charging system, generators from Scotland will pay “higher connection charges, chiefly as Transmission Network Use of System (TNUoS) charges, compared to generators elsewhere in Great Britain because of their distance from centres of demand” (Great Britain House of Lords EUC, 2008). To be able to transmit to the national grid network, 

Scottish producers would pay £21.59 per kilowatt (kW) (Jones, 2010). This amount is much higher than the charge imposed to producers in England because Scottish producers are farther away from areas of demand (Great Britain House of Lords, 2008b). TNUoS charging system was devised to stimulate generators to connect near areas of demand. However, renewable and conventional generators do not only pay for TNUoS charges but also for BSUoS (Balancing Services Use of System) charges for employing the National Grid as system operator (Great Britain House of Lords, 2008b). If renewable generation in Scotland will expand, BSUoS charges will also increase (Great Britain House of Lords, 2008b). With this as a possibility, it will be a hurdle for the electricity market because BSUoS charges do not vary by location currently (DECC, 2010). 

The current charging scheme may put Scotland off from generating renewables and hamper investments, especially that Scotland is a precious generator (Great Britain House of Lords, 2008b). If generators will increase renewables production with the local grid, not only will they be paying higher charges, there is also a more significant possibility for losses during transmission to and fro far distances (Great Britain House of Lords, 2008b). The Scottish government believes that networking charging regime will produce economic results than a transmission charging system (EDEM, 2010).

Generally, increasing renewable generation would involve technical, economic, political and ecological interventions. However, an external downside to increasing renewable generation within the Scottish transmission line is the possibility that it would reduce healthy competition within the British zone. While renewable generation is entirely promising for the environment, increasing it would affect the game drastically (Macalister, 2008).

Decreasing RE Generation

Decreasing renewable generation may not affect demand since conventional substitutes are still readily available. In other words, there will be no significant changes in the demand levels for renewable energy from different sectors outside Scotland, where it is potent. 

One crucial factor to consider is the fact that renewable energy is still highly unreliable so that increasing its production may not equate to demand satisfaction. Additionally, the country will have to depend on conventional resources to serve as a back-up, especially during peak demands. Therefore, decreasing renewable generation will only pronounce the importance of fossil fuels and other traditional energy resources for everyday consumption. 

Although if Scotland reduces its production of renewables, it may not inflict economic strains because conventional power plants will not have to be closed.   

Optimal Fraction of Renewable Energy 

“Currently only bioenergy and hydropower make significant contributions to meeting energy demand, followed by geothermal energy and wind power” (Great Britain House of Lords, 2008a). Scotland may produce approximately 63 GW of electricity from its renewable energy potential — from which 11.5 GW and 25 GW are from onshore and offshore wind respectively, 14 GW of both wave, 7.50 GW from the tidal stream, and 1.63 GW hydropower, and biomass, geothermal, etc. comprise the remaining proportion (see Table 2 for the corresponding capacities) (McDermott, 2010). The country’s current renewable energy capacity, which is only 3 GW comes mostly from onshore wind (McDermott, 2010). For this reason, concentrating on wind and marine power generation is optimal. The optimal fraction of current is to marine sources is 12:7. 

Onshore and Offshore Wind Energy

Fifty-six of Scotland’s 170 renewable plants are large wind farms; some is the largest onshore wind farms in the whole of Europe (Alldritt & Hopwood, 2010). Onshore wind represents Scotland’s significant resource potential (Scottish Executive, 2005). This explains why the country sources the most massive volumes of wind energy to several parts of Europe. By 2016, Viking Energy, a joint venture between the Shetland community and Scottish and Southern Energy (SSE), proposes to install 150, 3.6 MW turbines (Alldritt & Hopwood, 2010). This would result in the production of 2 billion units of energy annually (Alldritt & Hopwood, 2010). 

Nevertheless, even without optimization, onshore wind alone will already suffice in reaching the 2020 renewable target which is 17 TWh and an additional 20 TWh energy cap as a result of switching to renewable from conventional generation (RSPB, WWF, & FOE, 2006). Onshore wind has been estimated to produce 45 TWh for electricity use (RSPB, WWF, & FOE, 2006). Although these figures still have to be proven in practice because of there even a need to coping with the impacts of wind intermittency and for grid infrastructure upgrades (RSPB, WWF, & FOE, 2006).  

Aside from the onshore wind, however, offshore wind power in Scotland is also harnessed through two wind farms, Moray Firth and Firth of Forth (Carrell, 2009). These wind farms could generate 5 GW of electricity from 950 new wind turbines (Alldritt & Hopwood, 2010). 

Marine Energy (Tidal Stream and Wave Energy)      

 Wave and tidal stream sources are also abundant sources readily available for exploitation. Scotland’s marine power can deliver 1.3 GW. However, marine energy is still a premature technology in Scotland, making it a less explored renewable source (AEA, 2010). Nevertheless, SEA, an agency authorized to conduct to study wave and tidal energy, concluded that the country’s marine renewable sources could generate power between 1,000 MW and 2,600 MW, that is, taking into account the limits set within the study (AEA, 2010). It is worth-mentioning that Scotland develops the most advanced technologies that exploit its full potential for renewable energy production.

Optimal Energy Mix

Electricity generation will have to be de-carbonized through optimal use of renewable sources and fossil fuels to capture and store carbon (Scotland, 2009). If wind and potential marine capacity is fully realized, Scotland will be able to generate power more than UK needs. Wind and maritime power will be an optimal mix because they are the two most abundant and potent renewable sources in Scotland. It is only rational to make use of what is readily available. Scotland is less concentrated in producing solar and biofuel energy to provide for the heat and transport sectors which is why the country can globally affect the demand for renewable electricity usage instead. Electricity production and consumption yield the most massive quantities of sulfur dioxide and carbon dioxide (Powerful Solutions, 1999).

On another point, according to Scottish Renewables, a forum promoting renewable energy development and consumption, there is no optimal combination of different types of renewables in Scotland. It says that regardless of whether there is optimization, the 2020 target may still be achieved. Perhaps this is because renewable resources are conserved; and since the country is endowed with a wide variety of resources, it will be able to sustain a significant electricity market. Renewable energy is widely used for electricity usage, although in both the heat and transport sectors, more development will be necessary. Electricity only comprises 20% of energy consumption whereas heating and transport account for the remaining percentage (Scottish Renewables, 2011).

Additional Renewable Energy Storage Facilities

Energy storage facilities enable producers to satisfy an increasing demand by providing an adequate supply of energy stored from these facilities. Because the potential of Scotland can influence the demand curve, generators will have to produce more but still with the utmost operating efficiency. Hence, generators need to install additional storage facilities in potent locations and where possible, near areas of demand.

Storage for renewable energy is equally important as for conventional power. The intermittency of renewable resources makes storage even more critical, especially during periods where demand is high. If Scotland decides to increase its production, it will require additional storage facilities installed in prospective locations. Scotland already has advanced energy storage technologies such as fluid storage, advanced battery systems, mechanical systems, electro-magnetic systems, hydrogen for energy storage. Additional wind and marine power will be contained in extra pumped hydro storage and compressed air storage systems.  

The Western Isles is a good location for producing renewables. Since 1992, renewables development has already been conducted on the island. The place has been the “testbed for renewables and energy-saving technologies” so that it can become the capital for renewable energy generation particularly wind and marine power, in Europe (Department for Sustainable Communities, n.d.). Onshore wind farms in North Lewis could perform 150 MW installed capacity (Halcrow Group, 2009). Meanwhile, wave and tidal resources are a recent ongoing development in the Western Isles, and which can deliver an estimated total of 105 MW (Halcrow Group, 2009).

Using pumped hydro storage and compressed air storage systems will store the unharnessed wind potential in the Western Isles. Wind-powered hydro storage is the oldest energy storage technology for energy production. This method is practical for wind energy storage because it pumps water to the upper reservoir during low demands such that it will provide during the period of peak demands (Ernest, n.d.). Compressed air storage facilities could generate electricity when demand escalates by mixing natural gas and compressed air, stored primarily in underground caverns or abandoned mines, to combust as fuel (Ernest, n.d.). Tidal stream, on the other hand, will only need to be stored in a dam and released to generate electricity.

Conclusion

Scotland is one of those few developed nations which render efforts to moderate the impacts of climate change. With the aid of the most advanced technologies, renewable energy can become very reliable. The country proves this premise. Not only will it be able to attain its national goal to reduce carbon emissions, but it also provides other countries especially developed nations, which are significant pollutants but only care less about tapping their natural resources to reduce their carbon and other GHG emissions, the incentive that renewable energy is the only immediate solution to the worsening environmental condition. 

Wind and marine resources are well-provided in Scotland. With an estimated 36 GW of aggregate wind power and approximately 21 GW of both wave and tidal stream capacity, the optimal fraction of renewable energy sources in Scotland is 12:7 GW. Nevertheless, even without optimizing these resources for renewable generation, Scotland will still be able to affect demand for renewable energy in all sectors worldwide, that is if the country is faithful and bold enough to capitalize on them. 

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