ValuationandIntegrationofSolarEnergy太阳能评价与并

1、Valuation and Integration of Solar Energy: 太阳能评价与并网Early Results from the United States美国初期研究成果Ryan Wiser怀瑞恩Consultant to the Center for Resource Solutions资源解答中心专家Energy Foundation Workshop能源基金会研讨会Beijing, ChinaJuly 2, 1010Motivation 研究动机Increasing focus on solar as source of electricity:Growth in i

2、nterest in large-scale plants: 50 GW seeking interconnection in U.S., 10 GW in later stages of developmentDecision-makers need to understand electric system value of solar electricity (PV/CSP, w/ and w/o storage):Solar is variable/unpredictable: valuation will differ from conventional gen.Output var

3、iability/uncertainty studied for wind; little similar work on solarTwo areas of particular interest:Estimating the long-term electric system value of solar without storage given displacement in conventional gen. and optimal capacity expansionUnderstanding the technical and economic impacts of short-

4、term variability and uncertainty in PV output, and associated integration costsCurrent presentation does not include power quality timeframe2太阳能发电受到越来越多的关注美国对大规模电站的兴趣在提升：预期的并网需求超过50GW，约10GW的项目处于开发的后期阶段决策者需要认识到太阳能电力在电力系统中的价值（光伏/光热，有无储能）太阳能具有波动性/不可预测性：其评价方法将有别于常规能源针对风电出力变化/不确定性已有研究；太阳能这方面的研究却很少两个主要研究方

5、向：估算无储能太阳能在电力系统中替代常规电力的长期价值，及最佳容量了解光伏发电输出短期波动性和不确定性带来的技术和经济影响及并网成本目前的报告并不包括瞬时电能质量3Long Term Valuation长期价值4Value of an Electricity Generation Source Impacted By Multiple Factors电源价值受多种因素影响发电成本输电成本并网成本容量价值能源价值5Central Solar in Western U.S. Currently 3 cents/kWh More Valuable Than Wind Considering Ener

6、gy/Capacity Value考虑到能量/容量价值，美国西部集中式太阳能价值比风电高3美分/度Increased value due to coincidence with system peak, and therefore offset of higher-cost resources; benefits likely to be lower in China因与用电负荷高峰重合而增加了太阳能电力的价值，所以抵消了部分高成本；在中国，这方面的价值可能要低一些6Marginal Value of Solar Energy Drops with Penetration, But At Cu

7、rrent Levels, Added Value Is Considerable随着在总体电源中比重的增加，太阳能的边际价值会减少，但在目前的水平下，增值仍相当可观Renewable Penetration (% energy basis)可再生能源比重（发电量）Solar reduces peak load (high capacity value)Solar shifts peak load into night hours (low/no capacity value)Solar increasingly curtailed during peak production7For PV

8、(less so for CSP), Lower Transmission Needs Further Augment Added Market Value对于光伏（光热的情况不太一样），较低的输电需求进一步增加了它的市场附加值Figure shows estimated transmission cost for wind in US for large number of studies: 1 cent/kWh 基于大量研究，数据表明美国风电的输电成本高于1美分/度电Solar PV is modular and does not experience as strong economie

9、s of scale, allowing siting closer to load in many cases太阳能光伏是由一个个独立模板组成的，规模经济效益不如其他电源明显，并且很多情况下可以建在负荷周边8But, Solar without Storage Is Also Variable and, to a Degree, Unpredictable但是，无储能太阳能仍然是波动性较大的，某种程度上，不可预测Two key assumptions in previous analysisPerfect foresight (did not evaluate forecast error)

10、No sub-hourly variability (changes within hour require balancing)Costs for dealing with imperfect forecasts / sub-hourly variability = “integration costs”Wind integration well studied: cost $10/MWh Integration costs for solar poorly understoodNote: Focus here is on large-scale PV; CSP with and witho

11、ut storage a much smaller concern due to thermal inertia and storage之前分析的两个关键假设完美预测（预测误差未评估）不存在小时内波动 (需要平衡小时内波动)预测误差带来的成本/ 小时内波动= “并网成本”大量研究表明，风电并网成本 70% in less than 5-min兆瓦级电站在五分钟内变化可达70%以上Aggregation dramatically reduces variability; even within-plant variability at 1 min reduced with plant size

12、due to smoothing将众多电站作为整体考虑，则波动会大幅降低；同理，即便是单个电站范围内，一分钟内波动也随电站规模扩大而减少Source: Wiemken 2001Actual 5-min data from 100 PV plants in Germany. Aggregate output (P) is normalized by installed capacity (P installed)Aggregation Decreases Relative Variability When Sites Are Less Than Perfectly Correlated整体优势在

13、电站分布不是非常集中的情况下可以降低相对波动性Deltas: step changes from one averaging interval to the nextClear Sky Index: ratio of insulation if no clouds were present to measured insolationData: 1-min insolation data from 23 time-synchronized sites in the U.S.Source: Mills and Wiser 200915Forecasting for Solar Still Dev

14、eloping, But Is Much Better for Geographically Diverse Sites太阳能预测技术仍在发展，针对地理上分散分布的电站来讲预测效果更佳Clouds lead to forecast errors, and errors are greatest on partly cloudy daysForecast errors for geographically diverse sites smoothed by aggregation阴云导致预测偏差，多云/晴转阴的天气会加大误差。不同地区多电站形成的整体优势可以降低预测误差。Source: Lore

15、nz 2009Forecasts of solar output based on forecasts from the European Centre for Medium-Range Weather ForecastsLonger Forecast Horizon Increases Error远期预测误差增大 Assuming that current cloud conditions will not change (persistence forecast) is reasonable for short forecast horizons (1 h)Satellite or num

16、erical weather model based forecasts are better for longer forecast horizons对短期预报来说，假设当前云的条件不变(持续性预报) 是合理的（一小时内)卫星或数值天气模型预报，对长期预测更为合适。Multiple Sources of Reserves Can Mitigate Variability多种类型备用电源可以减轻出力波动Source Description TimescaleMechanical inertiaRotating mass of generatorInstantaneous, sustain fo

17、r 10sThermal inertiaSteam pressure in boiler10s, sustain for minsStorage/hydroTurbines not currently used10s to 10 minGas turbinesPeaking and backup turbines5 min to 20 minThermal plant overrunning Run station above max rated capacity Can run 3-10% over for few min without added stressIndustrial loa

18、d managementVoluntary interruptable loadsFast response but need to make provisions ahead of timeDomestic load management Automatic interruption of some loads (i.e. water heating)Instantaneous with proper equipment installedVoltage reductionLow voltage reduces loads Instantaneous, but degrades supply

19、Imported powerAdditional flow on tie lines Instantaneous, need to arrange/warnSpinning reserve Spare capacity on committed units Large thermal units can provide 2-4%/min reserve up to capacityBanked/pre-scheduled plantUnits on hot standby or scheduled earlyAvailable in 1-2 hours Source: Grubb 1991Ad

20、ditional Reserves Have Modest Cost for Diverse Solar Sites太阳能电站分散分布可以大大降低备用电源成本Source: Mills and Wiser 20105 close sites: 7,000 sq. km 25 site grid: 5 X 5 Site array with 40 km spacing between sites 40,000 sq. kmThese costs do not include cost of day-ahead forecast error. EnerNex (2009) estimated da

21、y ahead forecast costs to be $4-7/MWh for 800 MW PV/CSP combination, depending on assumptions for fuel costs这些成本不包含一日前预测误差。EnerNex (2009) 估算一日前预测成本，800兆瓦的光伏/光热组合规模下，大概是4至7美元每千度电， 这个成本也取决于对燃料成本的预期。19Conclusions from the United States美国经验总结Solar energy without storage, at low levels of penetration, can be quite valuable within the US energy system, suppo