SOLAR FEASIBILITY STUDY

Transcription

1 SOLAR FEASIBILITY STUDY KAKE SENIOR CENTER KAKE ALASKA June 24, 2015 Submitted By: BacGen Technologies, Inc, Maud de Bel

2 Executive Summary BacGen investigated the feasibility of installing a solar system at the Senior Center in Kake, AK. Only two options are recommended for consideration (with and without battery storage). A third option, finding alternatives for domestic hot water heating in the shoulder season, is discussed in the report but not considered economically viable. Option 1: 6 kw Grid Connected PV System Budget Cost of a 6 kw System $41,000 Annual Production kwh/y 5,747 % Offset (Assuming 25,000 kwh/y Consumption) 23% Annual Saving at $0.57/kWh (Assuming no losses to the grid) $3,276 Simple Payback (No Maintenance Included) Years 14 Payback with 6% Utility Escalator Years 10 Present Worth (Maintenance Included) Courtesy Alaska Energy Engineering $10, year Production (No Cell Degradation Included) kwh 114,940 Equivalent kwh Cost over 20 years (No Maintenance Included) $ 0.36 Option 1 is the simplest project to install but due to its limited size, will only offset about 23% of the power consumption. Its size is limited because in the summer, this system is expected to output about 4.5 kw of instantaneous power, while the load is also expected to be around the 5 kw mark. A larger PV system would back feed power to the grid at peak solar hours, for which credit is not available. Before installation can take place, the actual power consumption, instantaneous load and power quality need to be monitored. The inverter will switch off when power quality is poor. Another disadvantage is that this system will not be operational during a grid outage. Page 2

3 Option 2: 12 kw Battery Connected PV System Budget Cost of the System $72,000 Annual Production kwh/y 10,675 % Offset (Assuming 25,000 kwh/y Consumption) 43% Annual Saving at $0.57/kWh $6,085 Simple Payback (No Maintenance Included) Years 13 Payback with 6% Utility Escalator Years 10 Present Worth (Maintenance Included) Courtesy Alaska Energy Engineering $29, year Production (No Cell Degradation Included) kwh 213,500 Equivalent kwh Cost over 20 years (No Maintenance Included) $ 0.34 It is assumed that there are some economies of scale for installation of a 12 kw system compared to a 6 kw system. Therefore even though the price of batteries and charge controller needs to be included, over a 20 year period, the price of power would be $0.34/kWh instead of $0.36/kWh in Option 1 and the Present Worth is about three times higher because of the year-on-year saving on Utility cost. The $0.34 per kwh is a significant reduction (and will remain stable), compared to the $0.57/kWh paid today to the Utility (which is likely to increase over time). The advantage of this system is that upon a grid outage, this system can still be used. Dirty power does not affect operation of the inverter because this system is operated independent of the grid. AGM batteries were used for pricing, however those batteries may be sensitive to extended periods of non-use (such as in the winter in AK). Lithium batteries are less sensitive to this, but they are much more expensive. This aspect will require some additional consideration. Conclusion Depending on the level of funding, both options are considered viable. If funding of around $70,000 is available, than Option 2 is the preferred option since it offsets a larger amount of power at a lower per kwh price, and offers more security since it operates during dirty power and black-out periods. Page 3

4 Contents SOLAR FEASIBILITY STUDY... 1 Executive Summary... 2 Option 1: 6 kw Grid Connected PV System... 2 Option 2: 12 kw Battery Connected PV System... 3 Conclusion... 3 Introduction... 5 Scope of Work... 5 Findings from Site Visit, June 2, Lay-out Considerations... 9 Some Practical Considerations Option 1: Grid Connected Solar PV (no Batteries) Option 2: 12 kw Battery Back-up PV System Other Options Some Notes About The Lime Solar Proposal Option Option Option Summary Appendix A: Life Cycle Cost Analysis Page 4

5 Introduction Tlingit-Haida Regional Housing Authority (THRHA) owns and operates a Senior Center located at 177 Third Ave. Kake, AK (Lat/Long N W), on Kupreanof Island, southeast of Juneau. BacGen was asked to look into the cost and feasibility of building a solar PV system to offset power at the Senior Center. Kake, Alaska is a high-cost diesel-electric community served by Inside Passage Electrical Cooperative (IPEC). Current electrical rates are around $0.65/kWh (below 500 kwh per month) and $0.57 (for consumption above 500 kwh per month). IPEC will not purchase power back from the building owner and requires any PV power to be isolated from the grid 1 (i.e. there can be no net metering). The building is undergoing modernization. When completed, it will have 14 apartments for independentliving housing for low-income senior citizens. It will also have common spaces including congregate dining room, commercial kitchen, offices, ADA bathrooms, laundry room, basement garages, and storage areas. All apartments will have individual electric meters. The commercial kitchen will be on an independent electric meter too. The rest of the building will be on the common house meter. Only this meter is to be offset with electricity generated by solar PV. The Center will be heated with a wood pellet boiler, with propane boiler backup. Domestic hot water for apartments and most common spaces will be indirectly heated with the pellet boiler or propane back-up boiler. The purpose of the feasibility study is to investigate whether solar PV, with or without batteries, would be economically viable. Additionally, BacGen was asked to look into possibilities to offset some of the hot water generation with solar thermal, or air-to-water heat pumps. Scope of Work The work will include performing a Solar Feasibility study at the Kake Senior Center in Kake Alaska to determine feasibility, conceptual designs, integration strategies, and cost estimates for supplying costeffective solar energy solutions to lower operating costs at the Senior Center over a useful life of the building and solar components. The solar arrays are to be ground or wall mounted. The location for the solar array is along the skirted pile foundation on the south-facing, non-shaded side of the existing building, 178 feet in length, with space for panels up to 120 high. They are not to be roof mounted. Targeted capacity is 10,000 Watt minimum. The system will be parallel to the utility grid system, isolated with a non-grid tie inverter, and will not feed back into the utility grid system. The feasibility study shall look at intervention options including, but not limited to: 1. Solar PV to power a percentage of the common house meter with no battery storage 2. Solar PV to power a percentage of the common house meter with battery storage. 1 This statement needs to be investigated. It is important to know whether they will allow interconnection, if not net metering. Page 5

6 3. Solar PV to provide a percentage of the domestic hot water in combination with an air-to-water heat pump (Diaken Altherma or equal), for non-heating and shoulder-season months. The feasibility study for each option shall include: A cost-benefit analysis for each intervention option described above. An estimate of the percentage of solar energy provided in comparison to total energy required for the common house meter or domestic hot water production. An estimate of annual savings in dollars for each option, with standard inflation and maintenance factors applied. Adequate preliminary design to provide a rough order of magnitude cost estimate of plus or minus 10% of actual installed costs in 2015 dollars. A cost-estimate for each intervention option for consultation, final design work, inspection and commissioning with a solar installation contractor. An executive summary with conclusions and recommendations. Findings from Site Visit, June 2, 2015 During a site visit on June 2, it was found that the Center refurbishment is in advanced stages of completion. Figure 1 shows the pellet boiler (with green cover), the propane back-up boilers (behind pellet boiler) and the hot water storage tanks. Figure 1 Overview of Heat Plant in Senior Center Page 6

7 The intention is to run the pellet boiler during the winter, with domestic hot water being heated via a secondary loop. In the summer, when building heating is not necessary, it may be more cost effective to rely on the propane boiler (see Figure 2) just to heat domestic water (it will also be easier to respond to demand changes with the propane boiler). Figure 2 Propane Boilers Figure 3 Heat Recovery Ventilation Units Page 7

8 The air throughout the facility is conditioned through two heat recovery ventilation (HRV) units (Figure 3). Each has two separate fans (one 1,0000 cfm and one 500 cfm capacity, each with 0.48 kw motor size). Table 1 shows an estimation of future annual power consumption. Power consumption, in the past (when the common areas and individual units were all on a single meter) was in the 70,000 kwh/y range. Some limited information was available regarding control conditions of the various units. When electrical consumption of all important units is added up, the total is about 25,000 kwh/y, (about one third of previous consumption). Table 1 Power Consumption Estimation Rating Estimated Average Demand Estimated hours per year Total Annual Consumption (kwh/y) HRV-1 (Ventilation) 1,000 cfm 0.48 kw 0.4 kw 8,760 HRV cfm 0.2 kw 8, kw HRV-2 1,000 cfm 0.4 kw 4,000 7, kw HRV cfm 0.2 kw 4, kw Pellet Boiler Pump 0.6 kw 0.5 kw 5,840 2,920 Building Hot Water W 0.7 kw 1, Pump Pump, Hot Water Heat W 0.2 kw 6,000 1,200 Exchanger Hot Water Recirc 214 W 0.15 kw 8,760 1,314 Propane Boiler Pump W kw 2, LED Lights (Corridor 10.5W /ea kw 8,760 3,311 etc) LED Lights (Common 10.5W /ea kw Area) Washer/Dryer 500 W 0.5 kw 1, Misc (Outlets etc) 0.5 kw 6,995 TOTAL kw 25,000 Additionally, some information was obtained regarding the price, per million BTU, for heating purposes. Table 2 Price Comparison between Electricity, Propane and Wood Pellets at 2015 prices Electricity $0.57/kWh $167.01/MMBtu Propane $2.95/gallon $32.60/MMBtu Pellets $400/ton $24.39/MMBtu Page 8

9 Lay-out Considerations Figure 4 shows the area that is earmarked for the solar array on the south side of the building (the building materials will be removed). Figure 5 shows a layout proposal for a 6 kw (20 modules) or 12 kw (40 modules) system. A 12 kw system would span about 110 (of the available 178 length of the building). Figure 6 shows that in a 2 module landscape orientation, the maximum height of the array is 6. The system is perfectly south facing and there are no shading obstacles. Figure 4 Area Earmarked for Ground Mount Solar PV System Page 9

10 Figure 5 Overview of Solar Array Layout (6 kw and 12 kw) Page 10

11 Figure 6 Side view showing maximum height of 6 feet above ground Some Practical Considerations The installation of the pilings for the ground mount system is probably the most critical aspect considering the remote location. Because of the high wind loading, the depth of the piling is expected to be > 6 ft. Several techniques are used in the industry, but most require special machinery (for example the use of screws and hydraulic drilling). Digging holes and setting pilings in concrete may be the simplest but would require a lot of concrete (which is expensive in shipping cost). There are two Washington State based vendors who have installed solar systems in Alaska (Artisan and Western Solar ). Neither was prepared to quote a solar system claiming heavy workloads at this time. Alaska Marine Lines ships materials from Seattle, adding an estimated $0.15/Watt to the install price. EIC Engineers in Anchorage have provided stamped drawings for solar systems in the past (Brian, ; ). Since the power consumption of the future system will be much different than before, and is an unknown at this time, and also since the power quality will determine whether or not battery protection is required, the next step should be to do some type of power monitoring, for example using ). The power consumption and quality will determine the size and type of the system (battery or no battery). Figure 7 shows the acceptable voltage and frequency ranges for inverter operation (courtesy of Solaren.com). Page 11

12 Figure 7 Utility Grid Voltage and Frequency Limits for Residential (single Phase) for Grid-Ties PV Inverters Option 1: Grid Connected Solar PV (no Batteries) Option 1 was to look at a solar PV without the benefit of battery storage. The estimated size of the solar system should not exceed approximately 6 kw, since it was determined in Table 1 that the instantaneous demand will probably not exceed 4.5 kw. A solar size above 6 kw would back-feed electricity to the grid in the middle of the summer, for which there is no credit. Table 3 shows the monthly production for Kake (NREL Weather Data Source: (TMY2) ANNETTE, AK 162 mi). The solar radiation in kwh/ m 2 /day is a measure of the sun hours (at 100% efficiency). Table 3: Production and Offset Estimate of a 6 kw DC Solar PV System (Source: PVWatts, NREL) 6 kw system (14% losses) Month Solar Radiation AC Energy Consumption % offset Energy Value ( kwh / m 2 /day) (kwh) (kwh) $ January % $ 137 February % $ 151 March % $ 278 April % $ 359 May % $ 434 June % $ 411 July % $ 393 August % $ 412 September % $ 308 October % $ 186 November % $ 114 December % $ 93 Annual ,747 25,000 23% $3,276 Page 12

13 If the annual consumption is about 25,000 kwh/y, the monthly offset can be calculated. The monthly consumption was previously fairly stable for all seasons. It shows that a 6 kw system could offset about 30-35% of the consumption during the summer, provided there is no back-feed to the grid. On an annual basis, about 23% of electricity consumption can be offset by the solar PV system, with a value of about $3,276 in the first year. Table 4 shows typical hourly solar production in February, June and October against the hypothetical load profile. Figure 8 shows the hourly output, in kw AC Power from a 6 kw solar PV System in Kake. Note that only on a few occasions, the output exceeds 4.5 kw. There are 208 hours in the year that the power production exceeds 4,000 Watts AC and only 17 hours per year that the production exceeds 4,500 Watts, therefore the loss to the grid in this scenario is less than 1% on an annual basis. Table 4 Typical Demand and Solar Production of a 6 kw Grid Connected Solar System in Kake, AK in Different Seasons Hour Typical Demand (Hypothetical) Typical Solar Production on February 6 (Watts) Typical Solar Production on June 24 (Watts) Typical Solar Production on October 23 (Watts) (kw) , ,619 1, ,238 2,606 2, ,563 3, ,588 4,552 1, ,166 4, ,736 4, , , , Page 13

14 6,000 5,000 4,000 AC Output (Watt) 3,000 2,000 1,000-1/1/2015 0:00 2/1/2015 0:00 3/1/2015 0:00 4/1/2015 0:00 5/1/2015 0:00 6/1/2015 0:00 7/1/2015 0:00 8/1/2015 0:00 9/1/2015 0:00 10/1/2015 0:00 11/1/2015 0:00 12/1/2015 0:00 Figure 8 PVWatts Prediction of Typical Hourly Solar Output from a 6 kw PV System Page 14

15 Table 5: Cost Estimate for 6 kw Grid Connected System Unit Price Price Modules, Racking, Inverters, Wiring, Balance of System $3/W DC $ 18,000 Stamped Design $3,000 $ 3,000 Shipping $0.50/lbs $ 1,000 Ferry $ 1,000 Labor (Civil, Mechanical and Electrical) $ 15,000 Miscellaneous $ 3,000 TOTAL $ 41,000 Overall Price per Watt $ 6.83 Annual Saving $3,276 Simple Payback (No Maintenance Included) Years 13 Payback with 6% Utility Escalator Years year Production (No Cell Degradation Included) kwh 114,940 Equivalent kwh Cost (No Maintenance Included) $ 0.36 Maintenance is expected to be done in-house and generally consists of cleaning the modules, and periodically checking the output of the system. Adequate training should be obtained at time of installation. Inverters are typically under warranty for 10 years. An inverter replacement would cost about $2,500- $3,000 for this system. Appendix A contains a Net Present Worth analysis of the 6 kw and the 12 kw systems that includes the annual maintenance and inverter (/battery) replacement. Page 15

16 Option 2: 12 kw Battery Back-up PV System Table 6: Production and Offset Estimate of a 12 kw DC Solar PV System (Source: PVWatts, NREL) 12 kw System (20% losses) Month Solar Radiation ( kwh / m 2 /day) AC Energy Consumption % offset Saving ( kwh ) (kwh) ( $ ) January % $ 255 February % $ 280 March % $ 516 April , % $ 667 May 5 1, % $ 806 June , % $ 764 July , % $ 730 August , % $ 765 September , % $ 573 October % $ 345 November % $ 211 December % $ 172 Annual ,675 25,000 43% 6,085 Option 2 is a 12 kw system with battery storage. This system is not connected to the grid. Compared to Option 1, slightly higher losses were assumed due to the extra step of storing DC power in the batteries and then converting it to AC Power. Overall, this system would offset about 43% of annual power consumption. Table 7 shows a cost estimate for this system. Economies of scale were assumed for the electrical design, the labor cost and miscellaneous cost. The additional cost for batteries and charge controller was assumed to be $1/W DC. Due to the economies of scale, the overall price per Watt installed is lower in this option, and the 20-year cost of solar is expected to be $0.34/kWh (compared to 0.36/kWh in Option 1). Maintenance cost are expected to be similar to Option 1, however batteries are expected to be due for replacement after about 10 years. The replacement cost would obviously depend on the number of batteries installed in the first place. BacGen would recommend installing 16 batteries (AGM, 6 V, ~400 amph) which cost about $400/ea. Replacement of 16 batteries would be about $7,500 in 2015 prices. Page 16