The Electronic Newsletter of The Industrial Refrigeration Consortium Vol. 15 No. 2, 2015

Size: px
Start display at page:

Download "The Electronic Newsletter of The Industrial Refrigeration Consortium Vol. 15 No. 2, 2015"

Transcription

1 chan The Electronic Newsletter of The Industrial Refrigeration Consortium Vol. 15 No. 2, 2015 NET-ZERO ANALYSIS OF A REFRIGERATED WAREHOUSE PART 2: WIND & HYBRID In the last edition of the Cold Front (Vol. 15, No. 1), we defined a net-zero facility as being capable of producing at least as much energy on-site from renewable sources as it consumes over an annual cycle. We also introduced the end-use energy characteristics and temperature control requirements for a refrigerated warehouse that would serve as the target facility to assess the viability of achieving net-zero energy performance. This facility has an energy intensity of 157 kbtu/ft 2 -yr (1,783 MJ/m 2 -yr). Refrigerated Facility Overview The facility being analyzed is a refrigerated warehouse facility comprised of two (2) separate refrigerated docks, a cooler, and three (3) freezers totaling 166,875 ft 2 (15,500 m 2 ) of conditioned space. IRC Staff Director Doug Reindl 608/ or 608/ dreindl@wisc.edu Assistant Director Todd Jekel 608/ todd.jekel@wisc.edu Research Staff Dan Dettmers 608/ daniel.dettmers@wisc.edu John Davis jgdavis@epd.engr.wisc.edu In This Issue Net Zero Analysis of a 1-9 Refrigerated Warehouse Part 2: Wind & Hybrid Upcoming Ammonia Classes 2 Noteworthy 2 Energy Efficiency course 10 IRC Contact Information Mailing Address Toll-free University Avenue Phone 608/ Suite 3184 FAX 608/ Madison, WI info@irc.wisc.edu Web Address

2 The size and respective temperature set points for each of the spaces are given in Table 1. The annual total electrical energy consumption for this facility totals 7,717,792 kwh. Space Table 1 Refrigerated space specifications. Set Point F Area ft 2 Height ft Volume ft 3 Dock # , , F , ,000 Freezer Dock # , ,400 Cooler , ,200 0 F Freezer -2 47, ,976, F , ,688,000 Freezer Totals 166,875 6,669,600 Renewable Energy Technology Previously in Cold Front Vol. 15, No. 1, we evaluated the ability of a photovoltaic solar system to achieve net-zero energy for the refrigerated warehouse. There are a number of alternative renewable energy technologies that could be envisioned to meet the electrical energy needs of this refrigerated facility but we are limiting our attention in this second part of a two-part series to wind and a hybrid system of PV+wind energy generation. Both PV and wind energy technologies have been widely implemented at the utility scale sizes consistent with the renewable energy generation required for enabling this refrigerated warehouse facility to achieve net-zero energy. Upcoming Ammonia Courses & Events Introduction to Ammonia Refrigeration Systems October 14-16, 2015 Madison, WI Principles and Practices of Mechanical Integrity for Ammonia Refrigeration Systems November 4-6, 2015 Madison, WI Intermediate Ammonia Refrigeration Systems December 2-4, 2015 Madison, WI Process Safety Management Audits for Compliance and Continuous Safety Improvement January 13-15, 2016 Madison, WI Introduction to Ammonia Refrigeration Systems March 2-4, 2016 Madison, WI Ammonia Refrigeration System Safety April 13-15, 2016 Madison, WI 16 th Annual IRC R&T Forum May 11-12, 2016 Madison, WI Design of NH 3 Refrigeration Systems for Peak Performance and Efficiency September 12-16, 2016 Madison, WI Process Hazard Analysis for Ammonia Refrigeration Systems September 21-23, 2016 Madison, WI Noteworthy EPA Visit issues the IRC an website enforcement to access alert. presentations See full alert made at: at the 2011 IRC Research Plan and ahead Technology for the 16 th Annual Forum. R&T Forum: May 11-12, 2016 in Madison, WI. Send Mark items your of calendars note for now next for newsletter the 2012 to Todd IRC Jekel, Research todd.jekel@wisc.edu. and Technology Forum May 2-3, 2012 at the Pyle Center in Madison, WI. Send items of note for next newsletter to Todd Jekel, tbjekel@wisc.edu. 2

3 The analysis of renewable energy options for this facility, was conducted using the System Advisor Model (SAM) software package (NREL 2015). SAM allows users to simulate the energy and economic performance of various renewable energy technologies for a given location. The simulations performed with SAM aim to determine the necessary size of wind-alone and a combination of both PV+wind renewable energy generation. All renewable energy options are sized appropriately to produce sufficient electrical energy equal to or greater than the required annual energy for the facility (7,717,792 kwh). A critical assumption consistent with the analysis we conducted in Part 1 is that the utility grid will freely accept and credit the facility for all electrical energy generated during periods where the generation exceeds instantaneous electrical demand by the facility. Similarly, the utility grid will freely supply electrical energy during periods where the facility demand exceeds the generation from the on-site renewables so that on an annual basis, the net-metered electricity for the facility is zero. We realize this assumption is idealistic and not sustainable in the situation of growing deployment of renewable energy generation, including net-zero facilities, without some means of energy storage. Simulation Parameters Consistent with Part 1, the present analysis assumes the renewable energy generation capital is financed over a 25 year period, with an inflation rate of 2.5% per year. One of the economic metrics calculated by SAM is the Levelized Cost of Electricity (LCOE) which represents the average cost of electricity (kwh) generated by the renewable energy system over the 25 year time frame, adjusted for inflation. SAM calculates LCOE as follows: C AAAAAAAA,n C AAAAAAAA,n + i=1 (1 + d LLLL = nnn ) n Q n n i=1 (1 + d rrrr ) n n Where n = 25 yyyyy, C AAAAAAAA,n represents the cash flow after taxes in year n [$], d rrrr = 0.082, Q n = 0.025, aaa d nnn = (1 + d rrrr )(1 + e). The variable d nnn represents the nominal discount rate and d rrrr represents the real discount rate. The parameter e is an estimate of the inflation rate. Since the nominal discount rates vary, the LCOE results are shown parametrically for discount rates of 2%, 4%, and 6%. In addition to the economic parameters, location information and the associated estimates of resources (incident solar radiation) are required. Typical Meteorological Year (TMY) data was used in the PV analysis. Similar to the 2013 Cold Front article, we consider the viability of this net-zero facility for two different locations: Madison, WI and Phoenix, AZ. 3

4 Net-Zero with Wind When selecting wind turbines, it is essential to ensure the selected equipment will operate with high efficiency given the characteristics of the wind resource expected at the location of interest. The wind turbines in both locations are utility-scale machines with hub heights on the order of 80 m. The land requirement to support the wind energy generation option is larger than PV because of the required fall radius. Fall radius represents the spacing between each of the wind turbines such that the wind farm size is minimized, yet the potential energy loss of downwind turbines from upwind shadowing is mitigated. NREL recommends a minimum fall radius of 5-10 rotor diameters to optimize energy extraction (Denholm, 2009). The results for the wind turbine options below are based on a fall radius of 8 rotor diameters. Wind Results Madison, WI The wind energy generation option for Madison, WI consisted of four (4) Zond Z-50 turbines with a 750 kwdc rating each. Interestingly, the wind resource in Madison is sufficient to raise the capacity factor to nearly 32%. Key results for the net-zero wind system in Madison are shown below in Table 2. The installed cost of the wind energy option is $22,912,622 which is significantly higher than the PV option leading to a marked increase in the life-cycle cost of electricity as shown in Table 3. For comparison to PV, the average cost of electricity for the 25 year life was cents per kwh for the 2% discount rate. Table 2 Wind energy-based net-zero facility results for Madison. Annual Energy Generated (kwh) Installed Cost ($) Capacity Factor Land Area (acres) 8,363,820 22,912, % Table 3 LCOE for a wind energy-based system in Madison with varying nominal discount rates. Nominal Discount Rate LCOE ( /kwh) 2% % % Wind Results Phoenix, AZ The wind turbine analysis in Phoenix, AZ used twelve (12) Vestas V42 turbines with a 600 kwdc rating each. Wind energy in Phoenix struggled significantly more to meet annual demand, costing over twice as much as a similar setup in Madison, and six times more than the PV system in this same location. The high cost is a result of the low capacity factor shown in Table 4. Due to a lack of wind power in this region, a larger area 4

5 containing more wind turbines is required to generate the same amount of energy annually. Table 5 shows the LCOE over the same range of discount rates as considered for Madison. Table 4 Wind energy-based net-zero facility results for Phoenix. Annual Energy Installed Cost Capacity Land Area Generated (kwh) ($) Factor (acres) 8,373,479 54,390, % Table 5 LCOE for a wind energy-based system in Phoenix with varying nominal discount rates. Nominal Discount Rate LCOE ( /kwh) 2% % % When considering wind turbine power production, all locations clearly struggled during the hottest months of the year, when electrical demand peaked as evidenced by reviewing the results shown in Figure 1. Daily Power Production (kwh/day) Facility Power - Wind Systems 50,000 45,000 40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 - Feb-14 Mar-14 May-14 Jul-14 Aug-14 Oct-14 Nov-14 Jan-15 Month Actual Demand Madison, WI Phoenix, AZ Figure 1 Actual monthly average daily facility electrical energy consumption along with the generated electricity for wind to achieve net-zero. 5

6 Figure 2 below shows the monthly average daily power required for the refrigerated facility along with the monthly average daily electricity generated by PV and wind. During the summer months the production of electricity by PV is high while the wind energy is low. The opposite occurs during the wintertime, suggesting there might be synergy between the PV and wind. The hybrid system arrangement combines the two energy generation methods in order to evaluate how each supplements the other. Facility Power - Madison, WI 40,000 Daily Storage Charge (kwh/day) 35,000 30,000 25,000 20,000 15,000 10,000 5,000 - Feb-14 Mar-14 May-14 Jul-14 Aug-14 Oct-14 Nov-14 Jan-15 Month Actual Demand PV Simulation Wind Simulation Figure 2 Actual monthly average daily facility electrical energy consumption along with the generated electricity for PV and wind-energy systems to achieve net-zero. Hybrid PV & Wind Electricity Generation In some locations, the renewable energy resources can be synergistic. For example during periods of high PV production, the wind energy may be low and during periods of PV production, the wind energy is high. We explore this synergy by designing a hybrid PV+wind renewable energy generation to determine if the capacity factor can be increased over that of each technology in a stand-alone arrange and whether the life-cycle cost of electricity can be reduced. Hybrid Renewable Energy System Results - Madison, WI Based on the previous simulation results, the PV system before was capable of meeting the majority of the electrical demand, but would benefit from supplemental energy generation in the winter months. A combined PV-wind turbine case was created in SAM, where most of the power generation comes from the PV modules, as 6

7 they were capable of generating most of the electrical demand year-round. The same SunPower PV modules and inverters were selected, but the system design was scaled back. The PV system was designed to generate 4,000 kwdc, which would require 13,104 modules. This part of the system would require 17.6 acres of land to install. The design of the windfarm included two (2) Suzlon S turbines with a capacity of 600 kw each. This wind farm would take up 22.3 acres to install. Using the same weather data and economic parameters as before, the simulation results in an installed cost that is closer to the cost of only installing PV panels, but the added reliability of also having wind turbines installed for when solar generation isn t enough. All relevant parameters for the hybrid power generation simulation located in Madison are summarized in Table 6. The addition of wind energy production enabled an increase in the capacity factor compared to PV-alone; however, the cost of the system increased substantially. This is reflected in the higher LCOE values shown in Table 7. Table 6 Hybrid power generation net-zero simulation results for Madison. Annual Energy Generated (kwh) Installed Cost ($) Capacity Factor Land Area (Acres) 7,924,669 17,924, % 39.9 Table 7 LCOE for a hybrid power generation system with varying discount rates for Madison. Discount Rate Nominal LCOE (c/kwh) 2% % % Figure 3 shows the hybrid power generation system design discussed above creates an annual trend that is much more in phase with the actual demand of the facility. The maximum rate of energy deficit with the hybrid system is only 3,600 kwh/day, compared to 4,800 kwh/day with the PV system, and 13,500 kwh/day with the wind turbine system. Regardless, all simulated scenarios would require energy storage as a means to make up for power generation deficits at the facility. Hybrid Renewable Energy System Results - Phoenix, AZ Similar to the Madison analysis, the hybrid system design relied primarily on PV power generation along with supplemental energy from wind turbines to produce more reliable time dependent power generation. This specific design used four (4) Vestas V42 turbines coupled with 8,841 PV modules and nine (9) power inverters. Table 8 summarizes the hybrid system characteristics required in Phoenix, and Table 9 7

8 shows that the cost of this system is higher than both the PV-only system, although these metrics do not capture the true advantage of this system. Facility Power - Madison, WI Daily Storage Charge (kwh/day) 30,000 25,000 20,000 15,000 10,000 5,000 - Feb-14 Mar-14 Apr-14 May-14 Jun-14 Jul-14 Aug-14 Sep-14 Oct-14 Nov-14 Dec-14 Jan-15 Month Electric Demand Hybrid Figure 3 Simulated power generation using hybrid design compared to actual facility demand in Madison. Table 8 Hybrid power generation net-zero simulation results for Phoenix. Annual Energy Installed Capacity Land Area Generated (kwh) Cost ($) Factor (Acres) 7,844,033 24,055, % 58.8 Table 9 LCOE for a hybrid power generation system with varying discount rates for Phoenix. Discount Rate Nominal LCOE (c/kwh) 2% % % Figure 4 better depicts the advantage of using the hybrid system. Despite varying weather throughout the year, the rate of power production is fairly constant. Although analysis of hybrid designs can vary widely depending on the percentage of power that comes from PV and wind turbines, Phoenix produced the greatest and most consistent power production deficit of the two 8

9 locations. This is partly due to the lack of wind in this climate, shown in the wind only analysis. Daily Power Production (kwh/day) Facility Power - Phoenix, AZ 30,000 25,000 20,000 15,000 10,000 5,000 - Feb-14 Mar-14 May-14 Jul-14 Aug-14 Oct-14 Nov-14 Jan-15 Month Actual Demand Hybrid Figure 4 Simulated power generation using hybrid design compared to actual facility demand in Phoenix. Conclusions & Next Renewable Consideration In this edition of the Cold Front, we analyzed the use of wind energy and a hybrid system of PV+wind to achieve a net-zero refrigerated warehouse. The electric demand and energy used as a basis for sizing the renewable energy generation options was the same for both the Madison, WI and the Phoenix, AZ locations. In reality, those electrical use profiles would likely be different in the two locations. The analysis presented in Part 1 showed that PV can be used to achieve net-zero at a LCOE of approximately 14 /kwh in Madison, WI and approximately 10.5 /kwh in Phoenix, AZ. In this edition, the wind energy generation option was able to achieve a LCOE of approximately 24 /kwh in Madison, WI and approximately 59 /kwh in Phoenix, AZ. The high cost for Phoenix is reflective of the relative poor wind resource availability. Nonetheless, a PV+wind energy generation hybrid was analyzed and the LCOE yielded 23 /kwh in Madison, WI and approximately 30 /kwh in Phoenix, AZ. The simulated results also show that all of the renewable energy options must be grid-connected since there are significant periods when the facility electric demand exceeds the PV system electric production and vice versa. References NREL, 2015, System Advisor Model Software, Version

10 Achieving Energy Efficient Refrigeration Systems Sponsored by Wisconsin s Focus on Energy and hosted by Bassett Mechanical, this two-day course is your opportunity to learn proven techniques that lead to energy efficiency improvements for industrial refrigeration systems. The first day of the workshop includes a higher level overview aimed at ensuring participants understand the principles of industrial refrigeration systems and the basic approaches for establishing and implementing energy conservation measures for this infrastructure. The second day provides more depth in a number of specific energy conservation measures that have been field-proven for their ability to deliver significant energy savings and efficiency improvements in facilities that operate these custom-engineered systems. This course is intended for: End-user Utility manager/supervisors Refrigeration Operators Refrigeration and consulting engineers Refrigeration Contractors Utility personnel with interest or responsibility for food production and large refrigerated storage facilities This course will be held on November 11-12, 2015 at Bassett Mechanical 1215 Hyland Ave., Kaukauna, WI. Click here for more information and to register: 10