The economics of wind power with energy storage

We develop a nonlinear mathematical optimization program for investigating the economic and environmental implications of wind penetration in electrical grids and evaluating how hydropower storage could be used to offset wind power intermittence. When wind power is added to an electrical grid consisting of thermal and hydropower plants, it increases system variability and results in a need for additional peak-load, gas-fired generators. Our empirical application using load data for Alberta's electrical grid shows that costs of wind-generated electricity vary from $37 per MWh to $68/MWh, and depend primarily on the wind profiles of installed turbines. Costs of reducing CO₂ emissions are estimated to be $41–$56 per t CO₂. When pumped hydro storage is introduced in the system or the capacity of the water reservoirs is enhanced, the hydropower facility could provide most of the peak load requirements obviating the need to build large peak-load gas generators.     

Comprehensive evaluation of effects of straw-based electricity generation: A Chinese case

Greater use of renewable energy is being aggressively promoted to combat climate change by the Chinese government and by other governments. Agricultural straw is the kind of renewable energy source that would become a pollution source if it is not well utilized. We select the Shiliquan straw-based electricity generation project in Shandong Province, China as a case and assess environmental externalities of straw utilization in power plants by using life-cycle analysis. Results show that straw-based electricity generation has far fewer greenhouse gas (GHG) emissions than that of coal-based electricity generation. Improvement in the energy efficiency of equipment used for straw’s pretreatment would lead to a decrease of GHG emissions and energy consumption in the life-cycle of straw-based electricity generation. In case 400 million tonnes of wasted straw in China could be used as a substitute for 200 million tonnes of coal, annually the straw 291 Terrawatt hours (TWh) of electricity could be generated, resulting in an annual total CO₂ emissions savings of 193 million tonnes. Straw-based electricity generation could be a high-potential alternative for electricity generation as well as an incentive for utilizing wheat straw instead of burning it in the field.     

Potential of new lighting technologies in reducing household lighting energy use and CO2 emissions in Finland

Using light-emitting diodes (LEDs) can significantly reduce the current household lighting energy use in Finland during 2020–2050. Our calculations show that the potential of using LEDs in reducing household lighting energy use and corresponding CO₂ emissions in Finland during 2020–2050 can be significant. Reductions from the current level of Finnish household lighting energy use (1.8 TWh/a) were 59 % in 2020, 72 % in 2030 and 78 % in 2050, when a high LED penetration was assumed. Lighting energy savings in 2020 would mean a 1.3 % reduction from the current total electricity use in Finland (84.2 TWh/a). The starting point in 2012 was that the share of incandescent lamps was 32 % and the share of LED lamps 6 % of the total amount of lamps in an average household. Using the current average emissions factor (current electricity production structure), the saved amount of energy in 2020 means 234,000 tonnes of CO₂. Using the marginal emissions factor, the saved amount of energy means 920,000 tonnes of CO₂ emissions.     

Spatial variation of emissions impacts due to renewable energy siting decisions in the Western U.S. under high-renewable penetration scenarios

One of the policy goals motivating programs to increase renewable energy investment is that renewable electric generation will help reduce emissions of CO₂ as well as emissions of conventional pollutants (e.g., SO₂ and NO_x). As a policy instrument, Renewable Portfolio Standards (RPS) encourage investments in wind, solar and other generation sources with the goal of reducing air emissions from electricity production. Increased electricity production from wind turbines is expected to displace electricity production from fossil-fired plants, thus reducing overall system emissions. We analyze the emissions impacts of incremental investments in utility-scale wind power, on the order of 1 GW beyond RPS goals, in the Western United States using a utility-scale generation dispatch model that incorporates the impacts of transmission constraints. We find that wind investment in some locations leads to slight increases in overall emissions of CO₂, SO₂ and NO_x. The location of wind farms influences the environmental impact by changing the utilization of transmission assets, which affects the overall utilization of power generation sources and thus system-level emissions. Our results suggest that renewable energy policy beyond RPS targets should be carefully crafted to ensure consistency with environmental goals.     

The viability of balancing wind generation with large scale energy storage

This paper studies the impact of combining wind generation and dedicated large scale energy storage on the conventional thermal plant mix and the CO₂ emissions of a power system. Different strategies are proposed here in order to explore the best operational strategy for the wind and storage system in terms of its effect on the net load. Furthermore, the economic viability of combining wind and large scale storage is studied. The empirical application, using data for the Irish power system, shows that combined wind and storage reduces the participation of mid-merit plants and increases the participation of base-load plants. Moreover, storage negates some of the CO₂ emissions reduction of the wind generation. It was also found that the wind and storage output can significantly reduce the variability of the net load under certain operational strategies and the optimal strategy depends on the installed wind capacity. However, in the absence of any supporting mechanism none of the storage devices were economically viable when they were combined with the wind generation on the Irish power system.     

Lower electricity prices and greenhouse gas emissions due to rooftop solar: empirical results for Massachusetts

Monthly and hourly correlations among photovoltaic (PV) capacity utilization, electricity prices, electricity consumption, and the thermal efficiency of power plants in Massachusetts reduce electricity prices and carbon emissions beyond average calculations. PV utilization rates are highest when the thermal efficiencies of natural gas fired power plants are lowest, which reduces emissions of CO₂ and CH₄ by 0.3% relative to the annual average emission rate. There is a positive correlation between PV utilization rates and electricity prices, which raises the implied price of PV electricity by up to 10% relative to the annual average price, such that the average MWh reduces electricity prices by $0.26–$1.86 per MWh. These price reductions save Massachusetts rate-payers $184 million between 2010 and 2012. The current and net present values of these savings are greater than the cost of solar renewable energy credits which is the policy instrument that is used to accelerate the installation of PV capacity. Together, these results suggest that rooftop PV is an economically viable source of power in Massachusetts even though it has not reached socket parity.     

Estimating the electricity prices,generation costs and CO2 emissions of large scale wind energy exports from Ireland to Great Britain

The share of wind generation in the Irish and British electricity markets is set to increase by 2020 due to renewable energy (RE) targets. The United Kingdom (UK) and Ireland have set ambitious targets which require 30% and 40% of electricity demand to come from RE, mainly wind, by 2020, respectively. Ireland has sufficient indigenous onshore wind energy resources to exceed the RE target, while the UK faces uncertainty in achieving its target. A possible solution for the UK is to import RE directly from large scale onshore and offshore wind energy projects in Ireland; this possibility has recently been explored by both governments but is currently on hold. Thus, the aim of this paper is to estimate the effects of large scale wind energy in the Irish and British electricity markets in terms of wholesale system marginal prices, total generation costs and CO₂ emissions. The results indicate when the large scale Irish-based wind energy projects are connected directly to the UK there is a decrease of 0.6% and 2% in the Irish and British wholesale system marginal prices under the UK National Grid slow progression scenario, respectively.     

Assessing the value of wind generation in future carbon constrained electricity industries

This paper employs a novel Monte-Carlo based generation portfolio assessment tool to explore the implications of increasing wind penetration and carbon prices within future electricity generation portfolios under considerable uncertainty. This tool combines optimal generation mix techniques with Monte Carlo simulation and portfolio analysis methods to determine expected overall generation costs, associated cost uncertainty and expected CO₂ emissions for different possible generation portfolios. A case study of an electricity industry with coal, Combined Cycle Gas Turbines (CCGT), Open Cycle Gas Turbines (OCGT) and wind generation options that faces uncertain future fossil-fuel prices, carbon pricing, electricity demand and plant construction costs is presented to illustrate some of the key issues associated with growing wind penetrations. The case study uses half-hourly demand and wind generation data from South Eastern Australia, and regional estimates of new-build plant costs and characteristics. Results suggest that although wind generation generally increases overall industry costs, it reduces associated cost uncertainties and CO₂ emissions. However, there are some cases in which wind generation can reduce the overall costs of generation portfolios. The extent to which wind penetration affects industry expected costs and uncertainties depends on the level of carbon price and the conventional technology mix in the portfolios.     

The impact of variable demand upon the performance of a combined cycle gas turbine (CCGT) power plant

This paper presents experimentally measured data showing the impact of variable demand on a modern 800 MW CCGT plant. The results contrasting the performance of the plant when operating under optimum conditions with those measured when modulating the output to match dispatch instructions is presented and compared. These contrasts include the impact of step changes, continual modulation and both hot and cold starts of the plant. The results indicate the changes in fuel used per MWh, CO₂ emitted per MWh and the NOx emissions under different operating modes. From the subsequent analysis significant increases were recorded in both fuel used and CO₂ emitted when the plant departs from optimum operating conditions. When the plant is requested to cease generating due to over capacity on the system, major increases in the emissions of NOx, when required to restart generation together with large increases in the fuel used and CO₂ emitted per MWh, can be observed.     

CO2 emission and avoidance in mobile applications

The present paper analyzes the CO₂ emissions from mobile communications and portable wireless electronic devices in the Korea environment. The quantitative and qualitative contributions to CO₂ emission reduction of the substitution of renewable energy for traditional electricity as the power supply in these devices are also investigated.Firstly, the national CO₂ emission coefficient is temporarily estimated as 0.504 tCO₂/MWh, which can be regarded as the basis for calculating CO₂ emissions in mobile devices. The total annual CO₂ emissions from mobile devices is calculated as approximately 1.4 million tons, comprising 0.3 million tCO₂ for portable wireless electronic devices and 1.1 million tCO₂ for electric equipment required for mobile communication service.If renewable energy sources are substituted for traditional electricity sources in the supply for mobile devices, solar cell and wind turbine systems can reduce CO₂ emissions by about 87% and 97%, respectively. However, the use of fuel cell systems will only slightly reduce the CO₂ emissions. However, the use of the direct methanol fuel cell system can release 8% more CO₂ emissions than that emitted by using traditional electricity sources.     

Curtailed electricity and hydrogen in Association of Southeast Asian Nations and East Asia Summit: Perspectives form an economic and environmental analysis

This study examines how well producing hydrogen via electrolysis from curtailed electricity from renewables could fulfil environmental benefits against the cost of producing hydrogen via electrolysis in the context of the Association of Southeast Asian Nations (ASEAN) and the East Asia Summit (EAS). The cost of producing hydrogen via electrolysis ranges from less than USD² per kgH₂ when the electrolyser load factor is 1500 h or above to USD10 per kgH₂ or even higher when the electrolyser load factor is 500 h or lower. The amount of CO₂ emissions abated by hydrogen produced from curtailed electricity from renewables ranges from about 130 million tonnes to about 150 million tonnes for ASEAN and from about 18,000 million tonnes to about 19,000 million tonnes for EAS. Applying prevailing carbon prices to the CO₂ emissions abated, the possible monetised benefits of hydrogen produced via electrolysis from curtailed electricity from renewables range from about USD0.25 per kgH₂ to about USD9.00 per kg H₂ for ASEAN and from about USD0.50 per kgH₂ to about USD15.00 per kg H₂ for EAS. The results of the cost-benefit analysis suggest that the price of carbon needs to be about USD15 per tonne of CO₂ to justify hydrogen produced via electrolysis from curtailed electricity from renewables for both ASEAN and EAS. The results also suggest that high electrolyser load factors make hydrogen produced via electrolysis from curtailed electricity from renewables cost-competitive even under low carbon prices.     

LCI (Life cycle inventory) analysis of fuels and electricity generation in Singapore

This article offers a unique three-stage approach in LCI analysis for generating the environmental profile of electricity generation in Singapore. The first stage focuses on fuels delivered to Singapore, next on electricity generated from various types of power production plants. The third stage integrates the entire life cycle study. The final gate-to-gate results show that the total CO₂ emissions from the national grid are 455.6 kg CO₂ per MWh without any loss in transmission and 467.0 kg CO₂ per MWh with 2.5% losses. The results for the entire cradle-to-gate energy production are: 586.3 kg CO₂ per MWh without considering any losses and 601.0 kg CO₂ per MWh with 2.5% transmission loss. For the rest of the LCI, the cradle-to-gate results (per MWh) are kg 0.19 CO (carbon monoxide), 0.06 kg N₂O (nitrous oxide), 1.94–1.99 kg NO_x (nitrogen oxides), 2.94–3.01 kg SO_x (sulphur oxides), 0.064–0.066 kg VOC (volatile organic compounds) and 0.078–0.080 kg PM (particulate matters). From gate-to-gate, the results are 0.12 kg CO, 0.0016 kg N₂O, 1.42–1.46 kg NO_x, 2.56–2.62 kg SO_x, 0.033–0.034 kg VOC and 0.067–0.069 kg PM. Emissions of CO₂ from energy generation, climate change mitigation and policies for energy security are also discussed.     

Consequential environmental system analysis of expected offshore wind electricity production in Germany

Taking advantage of offshore wind power appears to be of special significance for the climate protection plans announced by the German Federal Government. For this reason, a comprehensive system analysis of the possible CO₂ reduction including the consideration of all relevant processes has to be performed. This goal can be achieved by linking a life-cycle assessment model of offshore wind utilisation with a stochastic model of the German electricity market. Such an extended life-cycle assessment shows that the CO₂ emissions from the construction and operation of wind farms are low compared with the substitution effects of fossil fuels. Additionally, in the German electricity system, offshore wind energy is the main substitute for medium-load power plants. CO₂ emissions from the modified operation and the expansion of conventional power plants reduce the CO₂ savings, but the substitution effect outweighs these emissions by one order of magnitude. The assumptions of the model, shown here to be above all CO₂ certificate prices, have a considerable influence on the figures shown due to a significant effect on the future energy mix.     

Markets for renewable energy and pollution emissions: Environmental claims,emission-reduction accounting,and product decoupling

Green electricity generation can provide an indirect route to cleaner air: by displacing generation from fossil fuels, green electricity can reduce emissions of CO₂ and conventional air pollutants. Several types of voluntary markets have emerged in the United States to take advantage of this relationship, including green electricity programs, carbon offsets, and renewable energy certificates. At the same time, regulators are favoring cap-and-trade mechanisms for regulating emissions. This paper describes the appropriate framing of environmental claims for green electricity products. We apply an accounting framework for evaluating claims made for capped pollutants, with entries for emissions, avoided emissions due to green electricity, and unused emission permits. This framework is applied in case studies of two major electric utilities that operate with green electricity programs and capped pollutants. The cases demonstrate that the relative magnitude of “unused permits” and “emissions avoided” is a key relationship for evaluating an emissions reduction claim. Lastly, we consider the evolution of the green electricity marketplace given the reliance on cap-and-trade. In this setting, pollution-emission products could be decoupled from one another and from the various green electricity products. Several positive consequences could transpire, including better transparency of products, lower certification costs, and more product choices.     

An approach for estimating the carbon emissions associated with office lighting with a daylight contribution

A method is proposed for estimating the electricity consumption (and associated carbon emissions) of a defined electrical-lighting configuration in an office building, accounting for the daylight contribution from windows and rooflights. Heat gains due to lighting for an average day in each month may be used to aid assessments of the effect of lighting systems on the cooling load, known to be high for office environments. For a typical 6-storey office building, annual energy savings for lighting of 56–62% and a reduction in CO₂ emissions of nearly 3 tonnes are predicted by changing the lighting and daylighting specifications for a defined “2005” scenario to those of a low-carbon “2030” scenario. The associated reduction in peak lighting-load, and hence heat gain due to lighting, is 3 W/m².     

Effect of heat-saving measures on the CO2 savings attributable to micro-combined heat and power (μCHP) systems in UK dwellings

This paper considers the relationship between heat-saving and micro-combined heat and power (μCHP) technological interventions for reducing the carbon footprint of existing domestic dwellings within the UK housing stock. The relationship between the annual heat requirement of individual dwellings and the CO₂ savings attributable to different μCHP systems is investigated (by means of predictive modelling based on heat and power demand datasets recorded on a 1-min time base for nine dwellings). An assessment is made of the effects of various heat-saving measures upon the annual CO₂ savings predictions for candidate μCHP system implementations, when applied to ‘domestic building variants’ (as defined within the Carbon Vision TARBASE research programme). The increasing application of heat-saving interventions serves to reduce the CO₂ savings solely attributable to a μCHP system. The magnitude of this effect is a function of the μCHP system's electrical efficiency and electrical power output. For example, a 1 kW prime mover of 10% electrical efficiency is predicted to reduce annual CO₂ emissions by 72 kg CO₂ for a dwelling with an annual heat requirement of 11.9 MWh, but if the identified set of heat-saving measures is implemented first the demand falls to 5.0 MWh and the μCHP system will actually result in an emissions increase of 100 kg CO₂ p.a. By comparison, relative savings of 467 and 294 kg CO₂ p.a. are predicted if this dwelling is fitted with a 1 kW prime mover of 30% electrical efficiency. Still greater savings are predicted for higher power output systems of high efficiency, but a relatively large proportion of the generated electricity (44–75% depending on the heat and electrical demand of the dwelling) must then be exported.     

Technical and cost assessment of energy efficiency improvement and greenhouse gas emission reduction potentials in Thai cement industry

The cement industry is one of the most energy-consuming industries in Thailand, with high associated carbon dioxide (CO₂) emissions. The cement sector accounted for about 20.6 million tonnes of CO₂ emissions in 2005. The fuel intensity of the Thai cement industry was about 3.11 gigajoules (GJ)/tonne cement; the electricity intensity was about 94.3 kWh/tonne cement, and the total primary energy intensity was about 4.09 GJ/tonne cement in 2005 with the clinker to cement ratio of around 82%. In this study, the potential application of 47 energy-efficiency measures is assessed for the Thai cement industry. Using a bottom-up electricity conservation supply curve model, the cost-effective electricity efficiency improvement potential for the Thai cement industry is estimated to be about 265 gigawatt hours (GWh), which accounts for 8% of total electricity use in the cement industry in 2005. Total technical electricity-saving potential is 1,697 GWh, which accounts for 51% of total electricity use in the cement industry in 2005. The CO₂ emission reduction potential associated with the cost-effective electricity savings is 159 kilotonne (kt) CO₂, while the total technical potential for CO₂ emission reductions is 902 ktonne CO₂. The fuel conservation supply curve model shows a cost-effective fuel-efficiency improvement potential of 17,214 terajoules (TJ) and a total technical fuel efficiency improvement potential equal to 21,202 TJ, accounting for 16% and 19% of the total fuel use in the cement industry in 2005, respectively. CO₂ emission reduction potentials associated with cost-effective and technical fuel-saving measures are 2,229 ktonne and 2,603 ktonne, respectively. Sensitivity analyses were conducted for discount rate, electricity and fuel prices, and exchange rate that showed the significant influence of these parameters on the results. Hence, the results of the study should be interpreted with caution.     

Modeling a clean energy standard for electricity: Policy design implications for emissions,supply, prices,and regions

The electricity sector is responsible for roughly 40% of U.S. carbon dioxide (CO₂) emissions, and a reduction in CO₂ emissions from electricity generation is an important component of the U.S. strategy to reduce greenhouse gas emissions. Toward that goal, several proposals for a clean energy standard (CES) have been put forth, including one espoused by the Obama administration that calls for 80% clean electricity by 2035 phased in from current levels of roughly 40%. This paper looks at the effects of such a policy on CO₂ emissions from the electricity sector, the mix of technologies used to supply electricity, electricity prices, and regional flows of clean energy credits. The CES leads to a 30% reduction in cumulative CO₂ emissions between 2013 and 2035 and results in dramatic reductions in generation from conventional coal. The policy also results in fairly modest increases on national electricity prices, but this masks a wide variety of effects across regions.     

The air quality and human health effects of integrating utility-scale batteries into the New York State electricity grid

In a restructured electricity market, utility-scale energy storage technologies such as advanced batteries can generate revenue by charging at low electricity prices and discharging at high prices. This strategy changes the magnitude and distribution of air quality emissions and the total carbon dioxide (CO₂) emissions. We evaluate the social costs associated with these changes using a case study of 500 MW sodium-sulfur battery installations with 80% round-trip efficiency. The batteries displace peaking generators in New York City and charge using off-peak generation in the New York Independent System Operator (NYISO) electricity grid during the summer. We identify and map charging and displaced plant types to generators in the NYISO. We then convert the emissions into ambient concentrations with a chemical transport model, the Particulate Matter Comprehensive Air Quality Model with extensions (PMCAM_x). Finally, we transform the concentrations into their equivalent human health effects and social benefits and costs. Reductions in premature mortality from fine particulate matter (PM_2.5) result in a benefit of 4.5 ¢ kWh⁻¹ and 17 ¢ kWh⁻¹ from displacing a natural gas and distillate fuel oil fueled peaking plant, respectively, in New York City. Ozone (O₃) concentrations increase due to decreases in nitrogen oxide (NO_x) emissions, although the magnitude of the social cost is less certain. Adding the costs from charging, displacing a distillate fuel oil plant yields a net social benefit, while displacing the natural gas plant has a net social cost. With the existing base-load capacity, the upstate population experiences an increase in adverse health effects. If wind generation is charging the battery, both the upstate charging location and New York City benefit. At $20 per tonne of CO₂, the costs from CO₂ are small compared to those from air quality. We conclude that storage could be added to existing electricity grids as part of an integrated strategy from a human health standpoint.     

Comparative assessment of greenhouse gas mitigation of hydrogen passenger trains

This paper examines a comparative assessment in terms of CO₂ emissions from a hydrogen passenger train in Ontario, Canada, particularly comparing four specific propulsion technologies: (1) conventional diesel internal combustion engine (ICE), (2) electrified train, (3) hydrogen ICE, and (4) hydrogen PEM fuel cell (PEMFC) train. For the electrified train, greenhouse gases from electricity generation by natural gas and coal-burning power plants are taken into consideration. Several hydrogen production methods are also considered in this analysis, i.e., (1) steam methane reforming (SMR), (2) thermochemical copper–chlorine (Cu–Cl) cycle supplied partly by waste heat from a nuclear plant, (3) renewable energies (solar and wind power) and (4) a combined renewable energy and copper–chlorine cycle. The results show that a PEMFC powertrain fueled by hydrogen produced from combined wind energy and a copper–chlorine plant is the most environmentally friendly method, with CO₂ emissions of about 9% of a conventional diesel train or electrified train that uses a coal-burning power plant to generate electricity. Hydrogen produced with a thermochemical cycle is a promising alternative to further reduce the greenhouse gas emissions. By replacing a conventional diesel train with hydrogen ICE or PEMFC trains fueled by Cu-Cl based-hydrogen, the annual CO₂ emissions are reduced by 2260 and 3318 tonnes, respectively. A comparison with different types of automobile commuting scenarios to carry an equivalent number of people as a train is also conducted. On an average basis, only an electric car using renewable energy-based electricity that carries more than three people may be competitive with hydrogen trains.