On the fluctuating power generation of large wind energy converters,with and without storage facilities

The power fluctuations and time duration patterns of large, hypothetical wind energy generators are analysed, using meteorological data for Denmark. It is found that the fluctuations, relative to a load which varies through the year in a manner similar to the actual load, are no greater than the fluctuations relative to a constant load (base-load application). The addition of a hypothetical short-term storage, capable of delivering the average power for 10–20 hr, makes the wind energy system as dependable as one large nuclear power plant, being capable of delivering the average power for about 70 per cent of the time. For full coverage by a wind energy system, an additional long-term storage facility must be added. It is found that for the wind energy conditions of the Danish site considered, a storage holding 40–60 days of average load and with a recovery percentage of 50, will be needed. Due to the energy losses in the storage systems, the installed capacity must be augmented by about 35 per cent. A few remarks are made about the prospects for developing suitable storage facilities, and about the cost of total wind energy systems relative to other means of producing electricity.     

The marginal cost of solar backup

The long-run marginal cost of providing electricity for solar heating and hot water systems is estimated for three utilities and compared with the cost of providing electricity to electric-only systems. All investment, fuel, and operating costs are accounted for. Hot water systems and combined heating and hot water systems are analyzed separately. It is found that the marginal cost for solar backup is no more than the marginal cost of electricity used for purely electric heating and hot water devices and also no more than the incremental cost of normal load growth. For the three utilities studied, there appears to be little basis for rate distinctions between solar devices using electric backup and electric-only heating and hot water devices. “Off-peak storage” heating and hot water devices have a much lower marginal cost than the standard systems; again, there appears to be no basis for distinguishing between solar and electric off-peak devices. Compared with average cost pricing, marginal cost pricing offers benefits to customers using solar and electric heat and hot water, especially if a separate lower rate is adopted for off-peak storage devices; these benefits can amount to several hundred dollars a year. Substantial savings in the use of oil and gas fuels can be achieved if residences using these fuels convert to solar systems, savings not necessarily achievable by a shift, instead, to electric systems.     

Economic analysis and optimal design of hydrogen/diesel backup system to improve energy hubs providing the demands of sport complexes

Energy crisis has led the communities around the world to use energy hubs. These energy hubs usually consist of photovoltics, wind turbines and batteries. Diesel generators are usually used in these systems as backup system. In this research, for the first time, an attempt is made to replace the traditional diesel only backup system with hydrogen only system and combined hydrogen and diesel backup system in hybrid photovoltaic and wind turbine energy systems. After introducing the available energy modeling tools and methods, explaining over advantages and disadvantages of each one, HOMER software was selected for this research. The simulations of this research show that using the traditional diesel generator as the backup system of the energy hub, creates a low cost system with the net present cost (NPC) of 2.5 M$ but also produces the highest amount carbon emission which is equal to 686 tons/year. The results of this study also indicate the hybrid renewable energy system which is supported by the hydrogen only backup system has the highest net present cost (NPC) and initial capital cost but reduces the maximum amount of carbon. The calculated NPC and carbon production of the energy hub using hydrogen only backup system are equal to 4.39 M$ and 55,205, respectively. On the other hand, the combined hydrogen/diesel backup system has reduced NPC compared with the hydrogen only backup system. The CO₂ production of this system is also lower than the diesel only backup system. The calculations indicate that the NPC and CO₂ production of the combined backup system are 3.53 M$ and 511,695 kg/yr. By comparing advantages and disadvantages of all 3 scenarios, the micro grid which uses the combined diesel/hydrogen backup system is selected as the most optimal system. The sensitivity analysis of the selected system shows that fluctuations of inflation rate along with the fluctuations of both fuel cells and electrolyzers capital cost do not affect the net present cost (NPC) considerably. On the other hand, fluctuations of capital cost of the main components like wind turbines affect the NPC much more than the others. If the inflation rate drops from 15% to 14% and wind turbine capital cost multiplier reduces from 1 to 0.8, the NPC value will drop by the value of 300,000 $.     

Flexibility in Europe's power sector — An additional requirement or an automatic complement?

By 2050, the European Union aims to reduce greenhouse gases by more than 80%. The EU member states have therefore declared to strongly increase the share of renewable energy sources (RES-E) in the next decades. Given a large deployment of wind and solar capacities, there are two major impacts on electricity systems: First, the electricity system must be flexible enough to cope with the volatile RES-E generation, i.e., ramp up supply or ramp down demand on short notice. Second, sufficient back-up capacities are needed during times with low feed-in from wind and solar capacities. This paper analyzes whether there is a need for additional incentive mechanisms for flexibility in electricity markets with a high share of renewables. For this purpose, we simulate the development of the European electricity markets up to the year 2050 using a linear investment and dispatch optimization model. Flexibility requirements are implemented in the model via ramping constraints and provision of balancing power. We found that an increase in fluctuating renewables has a tremendous impact on the volatility of the residual load and consequently on the flexibility requirements. However, any market design that incentivizes investments in least (total system) cost generation investment does not need additional incentives for flexibility. The main trigger for investing in flexible resources is the achievable full load hours and the need for backup capacity. In a competitive market, the cost-efficient technologies that are most likely to be installed, i.e., gas-fired power plants or flexible CCS plants, provide flexibility as a by-product. Under the condition of system adequacy, flexibility never poses a challenge in a cost-minimal capacity mix. Therefore, any market design incentivizing investments in efficient generation thus provides flexibility as an inevi complement.     

Determining optimal electricity technology mix with high level of wind power penetration

Notwithstanding its variability and limited controllability, wind power is expected to contribute strongly to electricity generation from renewable energy sources in the coming decades. Treating wind power as non-dispatchable by subtracting its output from the original load profile, results in a net load profile, which must be covered by conventional power generation. The screening curve methodology is a first approximation to find the optimal generation technology mix, based on relative cost levels. However, increased variability of the net load profile, due to wind power generation, strongly influences system operation. Therefore a static linear programming investment model is developed to determine the optimal technology mix. This alternative methodology shows a reduced capacity of inflexible generation after including operational constraints to properly account for net load variability. In order to illustrate this methodology, an example is set up, showing the sensitivity with respect to ramp rates of conventional generation, transmission interconnection and energy storage. The comparison of those different sources of system flexibility suggests that energy storage facilities better facilitate the integration of wind power generation.     

An economic feasibility analysis of photovoltaics power during urban load shedding time

A first-order cost analysis of Photovoltaics power generation and DG power generation for urban emergency load is presented. Six years field data of two DG sets installed at IIT, Delhi for emergency load have been thoroughly analysed to find out the requirements for such power generation model.The unit cost of emergency load energy is calculated using different parameters. These are the interest rate of commercial loan at present value of Indian market, IREDA loan facility to promote PV, the depreciation cost, operation and maintenance cost of PV and DG sets, and fuel cost of DG set. It is found that the unit cost of PV electricity is cheaper or comparable with that from DG power at present market price.     

Optimal green energy management for island resorts in Malaysia

This paper proposes optimum green energy systems for electricity generation of island resorts in Malaysia. A combination of solar energy and wind energy as intermittent renewable energy sources with a fuel cell (FC) system and a battery storage energy system as a backup to the green energy system is introduced for this study. This system is eco-friendly, economical over the long-term, highly sustainable and reliable. In addition, a diesel-based energy system as a non-green system is compared with the proposed green system. National Renewable Energy Laboratory's (NREL) HOMER software is used to determine and compare the optimal configuration green energy system with the diesel-based energy system in terms of net present cost, sensitivity analysis and pollutant gas emission. The feasibility and assessment of the proposed system is evaluated by utilizing the load profile and considering the geographical condition of a village (Juara village in Tioman Island) with approximately 30 chalets located in southern Malaysia. HOMER uses two types of load profiles for each given year. The first load profile is used during the presence of tourists, and the second profile is used when the locals are the main inhabitants of the island. The optimization management for the green energy system is performed through unit sizing to find the optimum power management analysis and to perform cost analysis of the system.The potential of renewable energy as well as a diesel-based energy system to meet the power demand for such a stand-alone system is considered. Technically feasible and economically viable green energy systems as prospective plans are explored in this study.     

Impact of hourly wind power variations on the system operation in the Nordic countries

The variations of wind power production will increase the flexibility needed in the system when significant amounts of load are covered by wind power. When studying the incremental effects that varying wind power production imposes on the power system, it is important to study the system as a whole: only the net imbalances have to be balanced by the system. Large geographical spreading of wind power will reduce variability, increase predictability and decrease the occasions with near zero or peak output. The goal of this work was to estimate the increase in hourly load‐following reserve requirements based on real wind power production and synchronous hourly load data in the four Nordic countries. The result is an increasing effect on reserve requirements with increasing wind power penetration. At a 10% penetration level (wind power production of gross demand) this is estimated as 1·5%–4% of installed wind capacity, taking into account that load variations are more predictable than wind power variations. Copyright © 2004 John Wiley & Sons, Ltd.     

An Integrated Feasibility Analysis of a Stand‐alone Wind Power System,including No‐energy Fulfillment Cost

Autonomous wind power systems are among the most interesting and environmentally friendly technological solutions for the electrification of remote consumers. However, the expected system operational cost is quite high, especially if the no‐load rejection restriction is applied. This article describes an integrated feasibility analysis of a stand‐alone wind power system, considering, beyond the total long‐term operational cost of the system, the no‐energy fulfilment (or the alternative energy coverage) cost of the installation. Therefore the impact of desired system reliability on the stand‐alone system configuration is included. Accordingly, a detailed parametric investigation is carried out concerning the influence of the hourly no‐energy fulfilment cost on the system dimensions and operational cost. Thus, by using the proposed method, one has the capability–in all practical cases–to determine the optimum wind power system configuration that minimizes the long‐term total cost of the installation, considering also the influence of the local economy basic parameters. Copyright © 2003 John Wiley & Sons, Ltd.     

Electricity supply on the island of Dia based on renewable energy sources (R.E.S.)

This paper presents a methodology for determining the specifications of an isolated R.E.S. power production system on an environmentally sensitive ecosystem. The wind and solar power constitute the primary power generation system and diesel generators act as backup. Real wind and solar potential measurements are used. The wind atlas of the island has been constructed. The specifications of the proposed system are optimized by the life cycle cost method. The renewable energy sources (R.E.S.) total annual energy production exceeds 90%. As a result, the dependence on the diesel generator set annual energy production is limited and the system’s operational cost is not practically influenced by the increasing fossil fuel prices. The introduction of a small size desalination plant for the production of drinkable water is also investigated. Both the available R.E.S. potential and the minimization of environmental impacts are considered for the siting of the equipment. The methodology of the present paper may be applied to other regions rich in R.E.S. potential, where the introduction of small size environmentally friendly isolated R.E.S. power systems is investigated.     

Generation Cost Assessment of an Isolated Power System With a Fuzzy Wind Power Generation Model

This paper presents a fuzzy set based modeling of wind power generation. The wind power generation has been solved by the proposed fuzzy generation for an island in Taiwan. The cost effectiveness of wind power generation is then evaluated by calculating the avoided generation cost of diesel generators. The load survey study has been performed to find the typical daily load patterns of various customer classes. With the typical load patterns and total energy consumption by each customer class, the load composition and daily power profile of the isolated power system are therefore derived. The wind power generation of eight wind turbines and the corresponding avoided generation cost is estimated by the fuzzy generation model according to the hourly wind speed. The power generation and the corresponding cost of diesel generators required to meet the system power demand with wind power generation have therefore been obtained. It is found that the wind power generation can economically and effectively substitute the generation cost of the diesel power plant and provide the partial power supply capability for the net peak load demand.     

Representation of variable renewable energy sources in TIMER,an aggregated energy system simulation model

The power system is expected to play an important role in climate change mitigation. Variable renewable energy (VRE) sources, such as wind and solar power, are currently showing rapid growth rates in power systems worldwide, and could also be important in future mitigation strategies. It is therefore important that the electricity sector and the integration of VRE are correctly represented in energy models. This paper presents an improved methodology for representing the electricity sector in the long-term energy simulation model TIMER using a heuristic approach to find cost optimal paths given system requirements and scenario assumptions. Regional residual load duration curves have been included to simulate curtailments, storage use, backup requirements and system load factor decline as the VRE share increases. The results show that for the USA and Western Europe at lower VRE penetration levels, backup costs form the major VRE cost markup. When solar power supplies more than 30% of the electricity demand, the costs of storage and energy curtailments become increasingly important. Storage and curtailments have less influence on wind power cost markups in these regions, as wind power supply is better correlated with electricity demand. Mitigation scenarios show an increasing VRE share in the electricity mix implying also increasing contribution of VRE for peak and mid load capacity. In the current scenarios, this can be achieved by at the same time installing less capital intensive gas fired power plants. Sensitivity analysis showed that greenhouse gas emissions from the electricity sector in the updated model are particularly sensitive to the availability of carbon capture and storage (CCS) and nuclear power and the costs of VRE.     

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.     

Power characteristics of a fuel cell micro‐grid with wind power generation

An independent micro‐grid connected with renewable energy has the potential to reduce energy costs, and reduce the amount of greenhouse gas discharge. However, the frequency and voltage of a micro‐grid may not be stable over a long time due to the input of unstable renewable energy, and changes in short‐period power load that are difficult to predict. Thus, when planning the installation of a micro‐grid, it is necessary to investigate the dynamic characteristics of the power. About the micro‐grid composed from 10 houses, a 2.5 kW proton exchange membrane fuel cell is installed in one building, and it is assumed that this fuel cell operated corresponding to a base load. A 1 kW PEM‐FC is installed in other seven houses, in addition a 1.5 kW wind turbine generator is installed. The micro‐grid to investigate connects these generating equipments, and supplies the power to each house. The dynamic characteristics of this micro‐grid were investigated in numerical analysis, and the cost of fuel consumption and efficiency was also calculated. Moreover, the stabilization time of the micro‐grid and its dynamic characteristics accompanied by wind‐power generation and fluctuation of the power load were studied. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Location of Swedish wind power—Random or not? A quantitative analysis of differences in installed wind power capacity across Swedish municipalities

The amount of installed wind power varies significantly across municipalities although the financial support for wind power production and the technology available is identical in all Swedish municipalities. This study analyses how local differences between municipalities, such as local wind prerequisites and socioeconomic conditions, might explain the establishment of wind power. The analysis is carried out for a cross section of Swedish municipalities. The time periods before and after 2006 are analyzed separately; and results reveal that the factors affecting wind power establishments are different between the two periods. In the later time period we found a statistically significant positive relationship between good wind resources and the presence of wind power as well as with the amount of wind energy installed. This result is consistent with the idea that the first wind power investments in Sweden were highly affected by individual wind energy enthusiasts, while in the more recent large-scale investments market-based judgments about future profitability may have become increasingly important. In addition, previous experience seems to be a factor that in itself facilitates additional future wind power establishments, thereby pointing to the role of accumulated institutional capacity.     

基于“风-光-储”测量数据融合的孤岛微电网一次调频参数优化模型

针对多种分布式电源接入孤岛微电网,使潮流分布更加复杂,导致微电网频率控制难以满足需求的问题,文章提出一种基于"风-光-储"测量数据融合的孤岛微电网一次调频参数优化模型。研究分布式电源参与微电网调频的调差系数和调频容量模型,基于"风-光-储"测量数据融合对"风-光-储"调频参数进行修正。考虑到"风-光-储"分布式电源调频的稳定性控制,以孤岛微电网中系统一次调频备用成本最小为目标,基于机会约束规划对调频参数进行优化,并采取基于拉丁超立方抽样的确定性转化方法进行模型的求解。仿真算例结果表明,文章所提出的优化模型,能够降低一次调频备用成本,提高了孤岛微电网的频率稳定性与经济性。     

Predicting performance of a renewable energy-powered microgrid throughout the United States using typical meteorological year 3 data

Natural disasters are increasing in frequency and cost throughout the United States. Long term power outages frequently result from natural disasters, which leads to higher reliance on inefficient and cost ineffective gasoline or diesel powered generators to meet energy needs. The development of deployable renewable energy-powered microgrids as mobile power sources would allow energy demands to be met in portable and effective way, while reducing diesel fuel consumption. Characterizing system performance of renewable energy-powered microgrids prior to deployment would allow a future system to be appropriately sized to meet all required electrical loads at a given intermittent diesel generator operational frequency. Appropriate sizing of renewable energy powered microgrids and backup diesel generators would decrease system operation and transportation costs as well as define the appropriate amount of fuel to be kept on hand. This paper focuses on developing figures that represent the quantity of external AC or DC load a microgrid could supply as a function of intermittent diesel generator operational frequency. Typical meteorological year 3 (TMY3) data from 217 Class I locations throughout the United States were inserted into an operational frequency prediction model to characterize the quantity of external AC and DC load the system could supply at intermittent diesel generator operational frequencies of 1%, 5%, 10%, 25%, and 50%. Ordinary block Kriging analysis was performed to interpolate AC and DC load power between TMY3 Class I locations for each diesel generator operating frequency. Figures representing projected AC and DC external load were then developed for each diesel generator operating frequency.     

Maximum wind energy contribution in autonomous electrical grids based on thermal power stations

Greek islands cover their continuously increasing electricity demand on the basis of small autonomous thermal power stations. This electrification solution is related with increased operational cost and power insufficiency, especially during summer. On the other hand, the stochastic behaviour of the wind and the important fluctuations of daily and seasonal electricity load in almost all Greek islands pose a substantial penetration limit for the exploitation of the high wind potential of the area. In this context, the present study is concentrated on developing an integrated methodology which can estimate the maximum wind energy contribution to the existing autonomous electrical grids, using the appropriate stochastic analysis. For this purpose one takes into account the electrical demand probability density profile of every island under investigation as well as the operational characteristics of the corresponding thermal power stations. Special attention is paid in order to protect the existing internal combustion engines from unsafe operation below their technical minima as well as to preserve the local system active power reserve and the corresponding dynamic stability. In order to increase the reliability of the results obtained, one may use extensive information for several years. Finally, the proposed study is integrated with an appropriate parametrical analysis, investigating the impact of the main parameters variation on the expected maximum wind energy contribution.     

Offshore wind turbine reliability and operational simulation under uncertainties

The fast‐growing offshore wind energy sector brings opportunities to provide a sustainable energy resource but also challenges in offshore wind turbine (OWT) operation and maintenance management. Existing operational simulation models assume deterministic input reliability and failure cost data, whereas OWT reliability and failure costs vary depending on several factors, and it is often not possible to specify them with certainty. This paper focuses on modelling reliability and failure cost uncertainties and their impacts on OWT operational and economic performance. First, we present a probabilistic method for modelling reliability data uncertainty with a quantitative parameter estimation from available reliability data resources. Then, failure cost uncertainty is modelled using fuzzy logic that relates a component's failure cost to its capital cost and downtime. A time‐sequential Monte Carlo simulation is presented to simulate operational sequences of OWT components. This operation profile is later fed into a fuzzy cost assessment and coupled with a wind power curve model to evaluate OWT availability, energy production, operational expenditures and levelised cost of energy. A case study with different sets of reliability data is presented, and the results show that impacts of uncertainty on OWT performance are magnified in databases with low components' reliability. In addition, both reliability and cost uncertainties can contribute to more than 10% of the cost of energy variation. This research can provide practitioners with methods to handle data uncertainties in reliability and operational simulation of OWTs and help them to quantify the variability and dependence of wind power performance on data uncertainties.