Technical considerations of excess energy in village hybrid power systems

Transcription

1 Technical considerations of excess energy in village hybrid power systems Kotzebue Wind Farm / AEA Alaska Rural Energy Conference Sep. 23,

2 Most Wind Energy Systems Have Excess Electricity Above ~8% average wind contribution, excess energy begins to appear because the variable energy source doesn t always match up with demand. Factors modulating excess energy include: Diurnal/monthly pattern of electrical load in community. Diurnal/monthly pattern of wind resource in community. Strength(class) of wind resource. Size of electrical load vs. diesel genset size. Minimum load on diesel gensets. Shape of wind speed distribution. Amount of wind generation installed. 2

3 Diurnal pattern of community electrical load vs. wind resource Electrical Load Wind Resource 3

4 Diurnal pattern of community electrical load vs. wind resource Electrical Load Wind Resource 4

5 Size of electrical load vs. genset size. Small, medium and large gensets Only large gensets 5

6 Class 3 wind regime vs. Class 7 Class 3 5 wind turbines Class 7 3 wind turbines 6

7 Minimum load on diesel gensets Hub community Large gensets 50% min load Large and med gensets 30% min load 7

8 Curtail individual turbines. Send to radiators dump load. Adjust maximum power set points. Store in batteries or flywheels. What to do with excess? Send to valued heat loads. Heat recovery loop vs. distributed electric boilers. Lightningfan guitarist with Tesla coil Fujian Province. Asiannewsphoto 8

9 Curtailment Not Recommended Max wind power = Village load minimum diesel set point in a curtailment only system. For example 185kw village load minus 45kw (30% of a 150kw genset) = 140kw of wind that can be brought onto the system. If both 100kW turbines could produce at full capacity, one turbine must be shut down to meet the max power limit. 200kW potential wind is reduced to 100kW. 9

10 Advanced turbine controls and dump loads Adjust maximum power set points on wind turbines on a minute by minute basis. Send power to radiators dump load. Prevents losses seen from wind turbine curtailment, but achieves no value/benefit from excess energy. 10

11 Store short periods (15 30 min) of excess electricity for use later. Offsets 35% efficient diesel generated electricity. Batteries, flywheels, super capacitors. Large amounts of storage can be too expensive for community scale systems. Electrical Energy Storage 11

12 Valued Heat Loads Offset oil fired boiler(s) in the community with excess electricity. An electric boiler can be placed on an existing power plant heat recovery loop if there are enough customers on the loop to use all the energy. Thermal mass is the piping and fluid of the HR loop itself. An electric boiler can also be placed in community building(s) too far away for efficient use of the HR loop. Residential heaters can be installed with ceramic thermal mass to store and release heat. The more heating nodes in a system, the more complex the controls. 12

13 The current preferred option is to find a place of value to divert excess energy. Secondary load systems can be designed to handle all the primary and secondary power in a community. Electrical storage options are developing and costs are expected to become more affordable over the next 5 10 years. Dump loads and advanced set point controls are better choices than curtailment. Installed Wind Capacity (kw) Total Wind Energy Produced (kwh) Summary of Options Excess Electricity Net Elec kwh Net Thermal kwh Control Method Fuel $4.5.gal Potential Benefit 300 (Hi Pen) 888, , , ,307 Elec Boiler or ETS units $240, % 300 (Hi Pen) 888, , ,873 0 Turbine max setpoint $206, % 300 (Hi Pen) 888, , ,873 0 Non value dump load $206, % 300 (Hi Pen) 489, ,227 0 Curtailment $169, % 300 (Hi Pen) 888, , , min Batt/FW storage $216, % 200 (Med Pen) 592, , , ,310 Elec Boiler or ETS units $180, % 200 (Med Pen) 592, , ,807 0 Turbine max setpoint $167, % 200 (Med Pen) 592, , ,807 0 Non value dump load $167, % 200 (Med Pen) 396, ,716 0 Curtailment $137, % 200 (Med Pen) 592,117 90, , min Batt/FW storage $173, % 13

14 St. Paul Wind/TDX Evaluating cost effectiveness: It s not simple 14

15 This analysis of cost effectiveness High level analysis that recognizes that true evaluation of costeffectiveness must incorporate site and system specific information. Focus on excess wind b/c we know that installing wind for the primary purpose of heat is not yet cost effective. 7/7/7 Rule: Class 7 wind $7,000/installed KW $7/gallon diesel fuel The goal of this analysis, and the ongoing dialogue with stakeholders, is to provide guidance to interested parties and to identify the best use of excess wind power 15

16 Assumptions change everything! Capital costs $150,000 Powerhouse control system upgrade $50,000 Community building boiler $75,000 Web based powerhouse control system for residential heat $10,000 Residential heating units Heating units efficiency Fuel oil units are 80% efficient Electrical resistance units are 100% efficient Financing Paid in cash, 0% interest Public loan financing, 5% interest Private loan financing, 7% interest Grant funding of utility improvement and 0/5/7% scenarios for marginal cost of each residential heaters Useful life Residential units 10 years All other components 20 years 16

17 A: This scenario looks at using excess power in a community facility as well as in residential buildings. The total cost is variable depending on the number of units; this analysis examines 20 to 60 residential units in addition to the one larger unit in a community facility. Scenario A B: This scenario considers only the marginal cost of each residential unit. The assumed cost is $10,000 per residential unit. Scenario B 17

18 Scenario A Community facility + residential Households need to displace enough diesel heating fuel to cover the cost of debt service in order for the project to break even. Cost of capital (debt service) Includes share of PH upgrades + in home heater Annual $/HH $/kwh 20 units $1, units $1, units $1, units $1, units $1, Cost of capital/kwh Cost of capital $/kwh # residential units 18

19 Scenario B Marginal residential only Household break even costs are highly dependent on both the cost of the avoided diesel heating fuel and the amount of diesel they are able to displace. Marginal cost per unit/year assuming 0% interest & 20% heating fuel displaced (245 gallons) Cost/gallon heating fuel Value of displaced diesel Required kwh Annual revenue requirement Displaced diesel minus revenue requirement Break even kwh cost $4.00 $ ,906 $1,000 ($21.74) $0.00 $5.00 $1, ,906 $1,000 $ $0.03 $6.00 $1, ,906 $1,000 $ $0.06 $7.00 $1, ,906 $1,000 $ $0.09 $8.00 $1, ,906 $1,000 $ $0.12 $9.00 $2, ,906 $1,000 $1, $0.15 Marginal cost per unit/year assuming 0% interest & 10% heating fuel displaced (122 gallons) $4.00 $ ,953 $1,000 ($510.87) ($0.13) $5.00 $ ,953 $1,000 ($388.59) ($0.10) $6.00 $ ,953 $1,000 ($266.30) ($0.07) $7.00 $ ,953 $1,000 ($144.02) ($0.04) $8.00 $ ,953 $1,000 ($21.74) ($0.01) $9.00 $1, ,953 $1,000 $ $

20 Variables that impact cost effectiveness 1. Number of units and system wind penetration. 2. Capital cost of residential units in rural communities are roughly twice that of the same units installed in urban places. Installed cost/unit has a significant impact on project economics. 3. Financing of projects. This analysis looked at three financing options: 0/5/7%. 4. Saturation rates in homes. Our modeling assumes 10% 20% of total heating demand in a home is displaced by excess wind. 5. Cost of diesel heating fuel. The higher cost the alternative heating fuel is, the more attractive use of excess wind becomes. 20

21 1. Determining the economics of using excess wind for heat in residential units requires site and system specific evaluation. 2. The first steps in evaluating investment in energy infrastructure should be: a. engage a qualified engineer to evaluate the local potential for using excess renewable energy for heat; b. assess the condition of the existing powerhouse and distribution system, often upgrades are needed to ensure successful integration of renewable energy; and c. assess the condition of the buildings/systems where excess renewable energy will be used for heat. 3. Gather detailed information. A community interested in using excess wind for heat will need site specific information to accurately assess the potential for economic benefit. Key variables are: a. Hourly wind data (10 min preferred) b. Daily temperature data c. Current diesel powerhouse system (Hourly/10 min load data) d. Community building heating demand (daily preferred) e. Average residential heating fuel consumption (monthly preferred) f. Cost of alternative heating fuel. Recommendations for communities interested in using excess wind for heat 21

22 PCE interactions Under the cost based method including excess renewable energy used for heat in total generation numbers has the effect of decreasing the total cost per kwh and thus potentially decreasing the PCE level for the community. Under the rate based method inclusion of the lower rate charged for excess power for heat could reduce the average rate thus reducing the community PCE level. Under the maximum PCE level method when a utility s cost of producing power is greater than $1/kWh the PCE level is set by using the following formula: [($1 PCE floor)*95%]. There are only a few communities in the program that have costs this high. If these communities were to develop a renewable energy resource that produced excess power for heat the result could be to reduce the total cost/kwh reducing the PCE subsidy level. 22

23 Rich Stromberg Cady Lister AKEnergyAuthority.org 23