Climate Change Technology Paper – Option 1 due April 28, 10:00 pm ENERGY TECHNOLOGIES OUTSIDE THE U.S. AND CANADA In order to understand the technologies that provide energy to our lives, it has been necessary to make certain assumptions about our society. For example, we only need to study loadfollowing capabilities of technologies if we decide that load following is necessary. Or, we only need to understand how solar panels work if we agree that CO 2 emissions are to be reduced, because this is a major premise that motivates the installation of large numbers of solar panels. During this course we have mainly constrained our attention to Canada and the United States and aimed to understand the technologies that have emerged as a response to these countries’ motivations and emission reduction goals. Now, it is time to question the motivations that have been adopted by the United States and Canada, and we shall do so by turning our focus internationally. Your assignment is to choose a country or region of the world that creates and uses energy in a meaningfully different manner from Canada and the United States and write a paper of 800 to 1200 words in length on these questions: 1. How is energy being created and used in the country of your choice? Please make your choice of country clear. Explains the energy systems, including main source of energy, main ways of transportation, and how the electricity grid looks like 2. What do you think is the main reason for this energy system to be different that North America’s system? Identify the main motivator for the choice of energy source and grid configuration 3. What roles do you think do climate change mitigation and adaptation play in the country of your choice? Which one do you think is more important in this country? You are encouraged to do this assignment in groups. Do understand that working in groups requires that the range, detail, and rigor of thought that you put into this assignment be (at least) twice or three times as impressive as if you did this alone. All group members will receive the same grade for their assignment. Paper Writing Guidelines In order to succeed on this assignment, please ensure that your paper meets the following guidelines: • Use specific evidence/analysis to support all claims/assertions: Assemble strong, specific, factual evidence to support your claims, including quoting, paraphrasing, and summarizing background information. • Introduce and discuss all quotations/paraphrases in detail: Each quotation must be introduced and discussed in detail to show the reader how it relates to your paper’s argumentative claims and overall thesis. • Use coherent, single-topic paragraphs: Ensure that each paragraph contains only one subject and its supporting evidence; add transition words between ideas and between paragraphs to show connections between the topics you discuss. • Be persuasive: The purpose of answering question 2 and 3 in your paper must be to convince/persuade the reader that your position/ opinion is a correct one, not merely to present information or discuss something widely accepted. • Use correct APA in-text citations and include a correct APA References list: For each quotation and paraphrase, you must include a correct in-text citation. These in-text citations must correspond to entries on the References list. • Use concise, direct, and active sentence structure: This paper should use a formal, academic style; however, the writing should not be verbose. Using the first person often helps to avoid the passive voice and keep sentences concise. Therefore, please feel free to use the pronoun “I”; however, avoid hedging statements like “I feel.” Final Paper - Evaluation Criteria CONTENT & ORGANIZATION ☐ Near the beginning, the paper includes a clear description of the topic being discussed. ☐ Each question in the paper description is answered clearly with specific claims throughout the paper ☐ Each of the paper’s claims is introduced and explained in detail. ☐ The paper includes evidence for each of its claims, including quotations, paraphrases, and summaries of information from secondary sources. ☐ All personal opinions in the paper are supported by evidence from course readings or another research ☐ Each quotation, paraphrase, and summary is introduced and discussed in detail. ☐ Each paraphrase is re-written completely in your own words and does not mimic the word choice or sentence structure of the original. ☐ Each quotation/paraphrase is accompanied by a correct APA citation (i.e. author, year, and, if applicable, page number). ☐ Transition words are used within and between paragraphs to show relationships between ideas. WRITING MECHANICS & CITATIONS ☐ The paper uses clear and correct sentence structure and writing mechanics. ☐ The paper includes correct in-text APA citations. ☐ The paper includes a correct APA References list. FORMATTING ☐ The paper is 800-1200 words long. ☐ The paper is in a typed electronic format. ☐ The paper includes a header with your name and the page number on every page. ☐ The paragraphs are indented, and there is no extra space between paragraphs. Energy xxx (2014) 1e15 Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy A roadmap for repowering California for all purposes with wind, water, and sunlight Mark Z. Jacobson a, *, Mark A. Delucchi b, Anthony R. Ingraffea c, d, Robert W. Howarth e, Guillaume Bazouin a, Brett Bridgeland a, Karl Burkart f, Martin Chang a, Navid Chowdhury a, Roy Cook a, Giulia Escher a, Mike Galka a, Liyang Han a, Christa Heavey a, Angelica Hernandez a, Daniel F. Jacobson g, Dionna S. Jacobson g, Brian Miranda a, Gavin Novotny a, Marie Pellat a, Patrick Quach a, Andrea Romano a, Daniel Stewart a, Laura Vogel a, Sherry Wang a, Hara Wang a, Lindsay Willman a, Tim Yeskoo a a Atmosphere/Energy Program, Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA 94305, USA Institute of Transportation Studies, U.C. Davis, 1605 Tilia St, Davis, CA 95616, USA c Department of Civil and Environmental Engineering, Cornell University, 220 Hollister Hall, Ithaca, NY 14853, USA d Physicians, Scientists, and Engineers for Healthy Energy, Inc., 436 14th Street, Suite 808, Oakland, CA 94612, USA e Department of Ecology and Evolutionary Biology, Cornell University, E145 Corson Hall, Ithaca, NY 14853, USA f K2B Digital, 2658 Griffith Park Blvd., Suite 612, Los Angeles, CA 90039, USA g H.M. Gunn Senior High School, 780 Arastradero Rd, Palo Alto, CA 94306, USA b a r t i c l e i n f o a b s t r a c t Article history: Received 16 December 2013 Received in revised form 21 June 2014 Accepted 26 June 2014 Available online xxx This study presents a roadmap for converting California's all-purpose (electricity, transportation, heating/ cooling, and industry) energy infrastructure to one derived entirely from wind, water, and sunlight (WWS) generating electricity and electrolytic hydrogen. California's available WWS resources are first evaluated. A mix of WWS generators is then proposed to match projected 2050 electric power demand after all sectors have been electrified. The plan contemplates all new energy from WWS by 2020, 80e85% of existing energy converted by 2030, and 100% by 2050. Electrification plus modest efficiency measures may reduce California's end-use power demand ~44% and stabilize energy prices since WWS fuel costs are zero. Several methods discussed should help generation to match demand. A complete conversion in California by 2050 is estimated to create ~220,000 more 40-year jobs than lost, eliminate ~12,500 (3800 e23,200) state air-pollution premature mortalities/yr, avoid $103 (31e232) billion/yr in health costs, representing 4.9 (1.5e11.2)% of California's 2012 gross domestic product, and reduce California's 2050 global climate cost contribution by $48 billion/yr. The California air-pollution health plus global climate cost benefits from eliminating California emissions could equal the $1.1 trillion installation cost of 603 GW of new power needed for a 100% all-purpose WWS system within ~7 (4e14) years. © 2014 Elsevier Ltd. All rights reserved. Keywords: Renewable energy Air pollution Global warming 1. Introduction This paper presents a roadmap for converting California's energy infrastructure in all sectors to one powered by wind, water, and sunlight (WWS). The California plan is similar in outline to one recently developed for New York State [39], but expands, deepens, and adapts the analysis for California in several important ways. * Corresponding author. Tel.: þ1 650 723 6836; fax: þ1 650 723 7058. E-mail address: jacobson@stanford.edu (M.Z. Jacobson). The estimates of energy demand and potential supply are developed specifically for California, which has a higher population, faster population growth, greater total energy use, and larger transportation share of total energy, but lower energy-use per capita, than does New York. The California analysis also includes originally-derived (1) computer-simulated resource analyses for both wind and solar, (2) calculations of current and future rooftop and parking structure areas and resulting maximum photovoltaic (PV) capacities for 2050, (3) air-pollution mortality calculations considering three years of hourly data at all air quality monitoring stations in the state, (4) estimates of cost reductions associated http://dx.doi.org/10.1016/j.energy.2014.06.099 0360-5442/© 2014 Elsevier Ltd. All rights reserved. Please cite this article in press as: Jacobson MZ, et al., A roadmap for repowering California for all purposes with wind, water, and sunlight, Energy (2014), http://dx.doi.org/10.1016/j.energy.2014.06.099 2 M.Z. Jacobson et al. / Energy xxx (2014) 1e15 with avoided air-pollution mortality and morbidity, (5) potential job creation versus loss numbers, (6) estimates of the future cost of energy and of avoided global-warming costs, and (7) WWS supply figures based on 2050 rather than 2030 energy demand along with a more detailed discussion of energy efficiency measures. It further provides a transition timeline and develops California-relevant policy measures. The California plan as well as the prior New York plan build on world and U.S. plans developed by Jacobson and Delucchi [37,38] and Delucchi and Jacobson [12]. Neither the California plan nor the prior New York plan is an optimization study; that is, neither attempts to find the least-cost future mix of generation technologies, demand-management strategies, transmission systems, and storage systems that satisfies reliability constraints. However, this study does discuss results from such an optimization analysis based on contemporary California energy demand. Several partial renewable-energy plans for California have been proposed previously. For example, California has a renewable portfolio standard (RPS) requiring 33% of its electric power to come from renewable sources by 2020. Williams et al. [77] hypothesized the infrastructure and technology changes need to reduce California emissions 80% by 2050. Wei et al. [76] used detailed projections of energy demand and a high-resolution resource capacity planning model to evaluate supply and demand alternatives that could reduce greenhouse-gas emissions in California 80% below 1990 levels by 2050. Although these efforts are insightful and important, the plan proposed here goes farther by analyzing a long-term sustainable energy infrastructure that supplies 100% of energy in all sectors (electricity, transportation, heating/cooling, and industry) from wind, water, and solar power (without fossil fuels, biofuels, or nuclear power), and hence provides the largest possible reductions in air pollution, water pollution, and global-warming impacts. In addition, unlike the other California studies, the present study quantifies air-pollution mortality and reduced costs due to reduced mortality and climate damage upon a conversion, along with job creation minus loss numbers. Further, it quantifies and differentiates between footprint and spacing areas required for the energy technologies and provides in-depth first-step policy measures for a conversion. 2. How the technologies were chosen? The WWS energy technologies chosen for California are existing technologies ranked the highest among several proposed energy options for addressing pollution, public health, global warming, and energy security [35]. That ranking study concluded that, for electricity; wind, concentrated solar, geothermal, solar PV, tidal, wave, and hydroelectric power (WWS) were the best overall options. For transportation, battery electric vehicles (BEVs) and hydrogen fuel cell vehicles (HFCVs), where the hydrogen is produced by electrolysis from WWS electricity, were the ideal options. Long-distance transportation would be powered by BEVs with fast charging or battery swapping (e.g., Ref.[50]). Heavy-duty transportation would include BEV-HFCV hybrids. Heating/cooling would be powered primarily by electric heat pumps. High-temperature industrial processes would be powered by electricity and combusted electrolytic hydrogen. Hydrogen fuel cells would be used only for transportation, not for electric power generation due to the inefficiency of that application for HFCVs. Although electrolytic hydrogen for transportation is less efficient and more costly than is electricity for BEVs, there are some segments of transportation where hydrogen-energy storage may be preferred over batteryenergy storage (e.g., ships, aircraft, long-distance freight). Jacobson and Delucchi [38] and Jacobson et al. [39] explain why this energy plan does not include nuclear power, coal with carbon capture, liquid or solid biofuels, or natural gas. However, this plan does include energy efficiency measures. 3. Change in California power demand upon conversion to WWS Table 1 summarizes global, U.S., and California end-use power demand in 2010 and 2050 upon a conversion to a 100% WWS infrastructure (zero fossil fuel, biofuel, or nuclear energy). The table was derived from a spreadsheet available in Ref. [40] using annually averaged end-use power demand data and the same methodology as in Ref. [38]. All end uses that feasibly can be electrified are assumed to use WWS power directly, and remaining end uses are assumed to use WWS power indirectly in the form of electrolytic hydrogen. Some transportation would include HFCVs, and some high-temperature industrial heating would include hydrogen combustion. Hydrogen would not be used for electricity generation due to its inefficiency in that capacity. In this plan, electricity requirements increase because all energy sectors are electrified, but the use of oil and gas for transportation and heating/cooling decreases to zero. The increase in electricity use is much smaller than the decrease in energy embodied in gas, liquid, and solid fuels because of the high efficiency of electricity for heating and electric motors. As a result, end-use power demand decreases significantly in a WWS world (Table 1). The 2010 power required to satisfy all end-use power demand worldwide for all purposes was ~12.5 trillion watts (terawatts, TW). Delivered electricity was ~2.2 TW of this. End-use power excludes losses incurred during production and transmission of the power. If the use of conventional energy, mainly fossil fuels, grows as projected in Table 1, all-purpose end-use power demand in 2050 will increase to ~21.6 TW for the world, ~3.08 TW for the U.S., and ~280 GW for California. Conventional power demand in California is projected to increase proportionately more in 2050 than in the U.S. as a whole because California's population is expected to grow by 35.0% between 2010 and 2050, whereas the U.S. population is expected to grow by 29.5% (Table 1). Table 1 indicates that a complete conversion by 2050 to WWS could reduce world, U.S., and California end-use power demand and the power required to meet that demand by ~30%, ~38%, and 44%, respectively. About 5e10 percentage points of these reductions (5.6 percentage points in the case of California) are due to modest energy-conservation measures. The EIA [21] growth projections of conventional demand between 2010 and 2050 in Table 2 account for some end-use efficiency improvements as well, so the 5e10 percentage point reductions are on top of those. Table S6 and Section 11 indicate that efficiency measures can reduce energy use in non-transportation sectors by 20e30% or more, which means that our assumption of a 5e10% demand reduction due to energy conservation on top of EIA [21] assumed modest demand reductions in the baseline projection is likely conservative. Thus, if the achieved demand reduction by 2050 exceeds our assumption, then meeting California's energy needs with 100% WWS will be easier to implement than proposed here. Another relatively small portion of the reductions in Table 1 is due to the fact that conversion to WWS reduces the need for upstream coal, oil, and gas mining and processing of fuels, such as petroleum or uranium refining. The remaining and major reason for the reduction in end-use energy is that the use of electricity for heating and electric motors is more efficient than is fuel combustion for the same applications [38]. Also, the use of WWS electricity to produce hydrogen for fuel cell vehicles, while less efficient than is the use of WWS electricity to run BEVs, is more efficient and cleaner than is burning liquid fossil fuels for vehicles [33,38]. Combusting electrolytic hydrogen is slightly less efficient but Please cite this article in press as: Jacobson MZ, et al., A roadmap for repowering California for all purposes with wind, water, and sunlight, Energy (2014), http://dx.doi.org/10.1016/j.energy.2014.06.099 M.Z. Jacobson et al. / Energy xxx (2014) 1e15 3 Table 1 Contemporary (2010) and projected (2050) end-use power demand (TW of delivered power) for all purposes by sector, for the world, U.S., and California if conventional fuel use continues as projected or if 100% conversion to WWS occurs. Energy sector Residential Commercial Industrial Transportation Total Percent change Conventional fossil fuels and wood 2010 (TW) Conventional fossil fuels and wood 2050 (TW) Replacing fossil fuels and wood with WWS 2050 (TW) World U.S. CA World U.S. CA World U.S. CA 1.77 0.94 6.40 3.36 12.47 0.39 0.29 0.78 0.92 2.37 0.030 0.024 0.048 0.103 0.206 3.20 2.00 11.2 5.3 21.6 0.49 0.37 1.02 1.20 3.08 0.041 0.032 0.066 0.141 0.280 2.6 1.9 8.9 1.7 15.1 (30%) 0.41 0.33 0.82 0.37 1.92 (37.6%) 0.033 0.030 0.053 0.042 0.157 (43.7) Source: Spreadsheets to derive the table are given in Ref. [40], who used the method of Jacobson and Delucchi [38] with EIA [21] end-use demand data. U.S (CA) population was 308,745,538 (37,309,382) in 2010 and is projected to be 399,803,000 (50,365,074) in 2050 [70], giving the U.S. (California) 2010e2050 population growth as 29.5% (35.0%). cleaner than is combusting fossil fuels for direct heating, and this is accounted for in Table 1. The percentage reduction in California power demand upon conversion to WWS in Table 1 exceeds the reduction in U.S. power demand because the transportation-energy share of the total is greater in California than in the U.S., and efficiency gains from electrifying transportation are greater than are those from electrifying other sectors. The power demand reduction in the U.S. exceeds that worldwide for the same reason. 4. Numbers of electric power generators needed and land-use implications How many WWS power plants or devices are needed to power California for all purposes assuming end-use power requirements in Table 1 and accounting for electrical transmission and distribution losses? Table 2 provides one of several possible future scenarios for 2050. Upon actual implementation, the number of each generator in this mix will likely shift e e.g., perhaps more offshore wind, less onshore wind. Environmental and zoning regulations will govern the siting of facilities. Development in “low-conflict zones,” where and biological resource value is low and energy resources are high, will be favored. Some such areas include lands already mechanically, chemically or physically impaired; brown fields; locations in or near urban areas; locations in the built environment; locations near existing transmission and roads; and locations already designated for renewable energy development. Decisions on siting should take into account biodiversity and wildlife protection but should not inhibit the implementation of the roadmap, because such a delay would allow fossil fuel plants to persist and cause greater damage to human and animal life. Solar and wind are the largest generators of electric power under this plan because they are the only two resources sufficiently available to power California on their own, and both are needed in combination to ensure the reliability of the grid. Lund [47] suggests an optimal ratio of wind-to-solar of 2:1 in the absence of load balancing by hydroelectric or CSP with storage. The present study includes load balancing by both, which makes it reasonable for us to assume larger penetrations of solar (in Table 2) than in that study. In addition, since a 100% WWS world will include more flexible loads than today, such as BEV charging and hydrogen production, it will be possible to shift times of load to match better peak WWS availability. Finally, power in many U.S. states will be dominated by wind (e.g., in Ref. [39], the proposed New York windto-solar ratio is 1.5:1 with hydroelectric used for load balancing). California, though, has a larger accessible solar resource than most states, and wind is more limited in terms of where it is available. In sum, the choice of a larger ultimate penetration of solar in California for 2050 was not based on an optimization study but on practical considerations specific to the state, the load balancing resources available, and the potential for large flexible loads in the state. Since a portion of wind and all wave and tidal power will be offshore under the plan, some transmission will be under water and out of sight. Transmission for new onshore wind, solar, and geothermal power plants will be along existing pathways but with enhanced lines to the greatest extent possible, minimizing zoning issues as discussed in Section S4. The footprint area shown in Table 2 is the physical area on top of the ground needed for each energy device (thus does not include underground structures), whereas the spacing area is the area between some devices, such as wind, tidal, and wave power, needed, for example, to minimize interference of the wake of one turbine with downwind turbines. Most spacing area can be used for open space, agriculture, grazing, etc. Table 2 indicates that the total new land footprint required for this plan is ~0.90% of California's land area, mostly for solar PV and CSP power plants (as mentioned, rooftop solar does not take up new land). Additional space is also needed between onshore wind turbines. This space can be used for multiple purposes and can be reduced if more offshore wind resources are used than proposed here. Fig. 1 shows the relative footprint and spacing areas required in California. 5. WWS resources available California has more wind, solar, geothermal, plus hydroelectric resource than is needed to supply the state's energy for all purposes in 2050. Fig. 2a and b shows estimates, at relatively coarse horizontal resolution (0.6 WeE  0.5 SeN), of California's onshore and offshore annual wind speed and capacity factor, respectively (assuming an RePower 5 MW, 126-m rotor turbine) at 100 m above the topographical surface. They are derived from threedimensional computer model simulations performed as part of this study. The deliverable power in California at 100 m in locations with capacity factor >30%, before excluding areas where wind cannot readily be developed, is ~220 GW (1930 TWh/yr). This translates to ~713 GW of installed power for this turbine operating in 7e8.5 m/s winds. Assuming two-thirds of the windy areas are not developable gives a technical potential of ~238 GW of installed capacity and 73.3 GW of delivered power. These resources easily exceed the 39.4 GW (345 TWh/yr) of delivered power needed to provide 25% of California's 2050 all-purpose energy demand in a WWS world (Table 2). Because of land-use exclusions in California, which depend on local zoning decisions, it may alternatively be useful to obtain a portion of onshore wind from Wyoming, where wind resources are enormous and underutilized, or from Oregon or Washington. Please cite this article in press as: Jacobson MZ, et al., A roadmap for repowering California for all purposes with wind, water, and sunlight, Energy (2014), http://dx.doi.org/10.1016/j.energy.2014.06.099 4 Energy technology Rated power of one unit (MW) Percent of 2050 power demanda met by technology Technical potential nameplate capacity (GW)b Onshore wind turbine Offshore wind turbine Wave device Geothermal plant Hydroelectric plant Tidal turbine Res. roof PV system Com/gov roof PV system Utility PV plant Utility CSP plant Total Total new land required 5 5 0.75 100 1300 1 0.005 0.10 50 100 25 10 0.5 5 3.5 0.5 8 6 26.5 15 100 238 166 7.5 187.1 20.9 7.4 83.1 55.3 4122 2726 Assumed installed nameplate capacity of existing þ new units (GW) Percent of assumed nameplate capacity already installed 2013 Number of new units needed for California Footprint for new units (percent of California land area)c Spacing for new plants/devices (percent of California land area) 25,211 7809 4963 72 0d 3371 14,990,000e 533,700e 3450f 1226f 624,407 4.42 0 0 21.8 100 0 1.66 1.17 0.37 0.0 3.4 0.000078 0.000024 0.00065 0.0061 0 0.00024 0.139 0.099 0.320f 0.579 1.14 0.90g 2.77 0.859 0.031 0 0 0.0031 0 0 0 0 3.67 2.77h 131,887 39.042 3.723 9.188 11.050 3.371 76.237e 54.006e 173.261 122.642 Rated powers assume existing technologies. The percent of total demand met by each device assumes that wind and solar are the only two resources that can power California independently (Section 5) and that they should be in approximate balance to enable load matching (Sections 6 and S3). Because of California's extensive solar resources, solar's total share is higher than that of wind's. The number of devices is calculated as the California end-use power demand in 2050 from Table 1 (0.157 TW) multiplied by the fraction of power from the source and divided by the annual power output from each device, which equals the rated power multiplied by the annual capacity factor of the device and accounting for transmission and distribution losses. The capacity factor is determined for each device as in Ref. [40]. Onshore wind turbines are assumed to be located in mean annual wind speeds of 7.5 m/ s and offshore turbines, 8.5 m/s [17]. These mean wind speeds give capacity factors (before line losses) of 0.338 and 0.425, respectively, for the 5-MW turbines with 126-m diameter rotors assumed. Footprint and spacing areas are similarly calculated as in Ref. [40]. Footprint is the area on the top surface of soil covered by an energy technology, thus does not include underground structures. Transmission and distribution losses for onshore wind are assumed to range from 5 to 15%; those for offshore and all other energy sources; 5% due to the proximity of offshore to load centers. a Total California projected end-use power demand in 2050 is given in Table 1. b Onshore wind, offshore wind, tidal, and wave estimates are derived in Section 5. Rooftop residential and commercial/government PV estimates are derived in Section S2. The rest is from Ref. [46]. The “technical” potential accounts for the availability of each resource (e.g., wind speed, solar insolation), the performance of the technology, topographic limitations, and environmental and land-use constraints on siting. The technical potential does not consider market or economic factors. It also treats each technology in isolation, and not as part of a system, with the result that, for example, some of the technical potential for CSP and some the technical potential for utility PV might be based on the same land. The potential for hydro in Ref. [46] was for hydro beyond existing hydro, so that was added to existing hydro here. c The total California land area is 404,000 km2. d California already produces about 90.6% (4.98 GW of delivered power in 2010) of the hydroelectric power needed under the plan (5.495 GW of delivered power in 2050). The remaining hydro can be obtained as described in the text. e The average capacity factors for residential and commercial/government solar are estimated in Section S4. The nameplate capacity of installed rooftop solar PV is estimated in Section S2. f For utility solar PV plants, nominal “spacing” between panels is included in the plant footprint area. The capacity factor assumed for utility PV is estimated in Section S4. The capacity factor for CSP is 21.5%. These capacity factors assume that most utility PV and CSP are in desert areas. g The total footprint area requiring new land is equal to the footprint area for new onshore wind and geothermal plus that for utility solar PV and CSP plants. Offshore wind, wave and tidal are in water, and so do not require new land. Since no new hydroelectric plants are proposed here (hydro's capacity factor is assumed to increase), hydro does not require new land. The footprint area for rooftop solar PV does not entail new land because the rooftops already exist and are not used for other purposes (that might be displaced by rooftop PV). h Only onshore wind entails new land for spacing area. The other energy sources either are in water or on rooftops, or do not use additional land for spacing. Note that most of the spacing area for onshore wind can be used for multiple purposes, such as open space, agriculture, grazing, etc. M.Z. Jacobson et al. / Energy xxx (2014) 1e15 Please cite this article in press as: Jacobson MZ, et al., A roadmap for repowering California for all purposes with wind, water, and sunlight, Energy (2014), http://dx.doi.org/10.1016/j.energy.2014.06.099 Table 2 Number, capacity, footprint area, and spacing area of WWS power generators needed to provide California's total annually averaged all-purpose end-use power demand in 2050, accounting for transmission, distribution, and array losses. Ref. [40] contains spreadsheets used to derive the table. M.Z. Jacobson et al. / Energy xxx (2014) 1e15 5 Fig. 1. Spacing and footprint areas required, from Table 2, to repower California for all purposes in 2050. The dots do not indicate the actual location of energy farms. For wind, the small red dot in the middle is footprint on the ground (not to scale) and the green or blue is space between turbines. For others, footprint and spacing are the same. For rooftop PV, the dot represents the rooftop area needed. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Dvorak et al. [17] mapped the West Coast offshore wind resources at high resolution (Supplemental information, Fig. S1). Their results indicate that 1.4e2.3 GW, 4.4e8.3 GW, and 52.8e64.9 GW of deliverable power (accounting for exclusions) could be obtained from offshore wind in California in water depths of
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