ELG 4126 DGD Sustainable Electrical Power Systems

Transcription

1 ELG 4126 DGD Sustainable Electrical Power Systems Winter 2015

2 DGD Introduction TA: Viktar Tatsiankou (PhD student) Objectives of the DGD: to teach students the economics of the distributed energy generation to assist students with the background information for case studies to have fun! The DGD is worth 15% of the course There will be 2 or 3 quizzes based on the DGD material DGD - ELG

3 Outline Distributed resources Distributed generation Grid resources Demand-side resources Electric utility rate structure Standard residential rates Residential time-of-use (TOU) rates Demand charges Demand charges with a ratchet adjustment Load factor Real-time pricing DGD - ELG

4 Distributed generation Generation of electric power by a variety of small-scale producers (up to 50 MW) located close to the point of use Examples: Wind turbines Solar farms Fuel cells Mini-hydro DGD - ELG

5 Grid resources Grid resources: advantages of distributed generation Increase grid capacity Decrease grid losses Grid-site storage Improved power factor Reduced connection losses DGD - ELG

6 Demand-side resources Demand-side resources: how can we use electricity more efficiently? Efficient lighting Appliance efficiency Heat pumps Motor controls Load shifting Absorption cooling DGD - ELG

7 Demand-side resources Demand-side resources: how can we use electricity more efficiently? Efficient lighting Appliance efficiency Heat pumps Motor controls Load shifting Absorption cooling DGD - ELG

8 Electric utility rate structures Essentially, how much does the electricity cost Varies considerably depending on the type of customers, time of day, time of year, place of use, etc. DGD - ELG

9 Standard residential rates Example of standard residential electric rate This is an inverted block rate structure (designed to discourage excessive consumption) Table 1. Example of the standard residential rates DGD - ELG

10 Standard residential rates Example of standard residential electric rate This is an inverted block rate structure (designed to discourage excessive consumption) Table 1. Example of the standard residential rates Power is measured in W or J/s Energy is measured in J or W s 1 J = 2.78 x 10-7 kw h 1 kw h = 3.60 x 10 6 J DGD - ELG

11 Example 1 Suppose that a customer subject to the rate structure in Table 1 uses 1200 kwh/month during the summer. a) What would be the total cost of electricity ($/month, ignoring the monthly service charge)? b) What would be the value ( /kwh) of an efficiency project that cuts the demand to 900 kwh/month? Table 1. Example of the standard residential rates DGD - ELG

12 Example 1 (Solution) a) The total monthly bill includes for a total of , , $ $ $ = $129.68/month b) If the demand is reduced to 900 kwh/month, the bill would be 700 $ $ = $84.34/month The savings per kwh is ($ $84.34)/300 kwh = $0.1511/kWh DGD - ELG

13 Residential time-of-use rates Example of residential time-of-use (TOU) rates Implemented to shift the customers loads away from the daily energy peak Solar installation generation well coincides with the summer energy demand peak Table 2. Example of the time of use rates DGD - ELG

14 Example 2 During the summer a rooftop PV system generates 10 kwh/day during the off-peak hours and 10 kwh/day during the on-peak hours. Suppose that the customer uses 2 kwh/day on-peak and 18 kwh/day off-peak. That is, the PV generates 20 kwh/day and the household consumes 20 kwh/day. For a 30-day month in the summer, find the electric bill for this customer if the TOU rates of Table 2 apply. DGD - ELG

15 Example 2 (Solution) During the on-peak hours, the customer generates 10 kwh and uses 2 kwh, so there would be a credit of On-peak credits = 8 kwh/day $ /kWh 30 day/month = $47.50/month During the off-peak hours, the customer generates 10 kwh and uses 18 kwh, so the bill for those hours would be Off-peak bill = 8 kwh/day $ /kWh 30 day/month = $20.43/month So the net bill for the month would be Net bill = $20.43 $47.50 = $27.07/month (customer is making money) DGD - ELG

16 Demand charges Usually applies to industrial or commercial entities Based on the highest (typically monthly) power drawn (averaged over a 15 min period) For example, if the peak power draw is 100 kw over 15 min in June, demand charges are $900 for that month. Table 3. Example of the demand charges DGD - ELG

17 Demand charges with a ratchet adjustment Problem with demand charges Monetary significant for one month of the year No sufficient for the utility to pay for the peaking power plant they had to build to supply the load Solution is to implement a ratchet adjustment into the demand charges Benefits Huge penalties for customers who add a few kwh to their load right at their annual peak Gives incentive for customers to reduce their annual peak energy demand DGD - ELG

18 Example 3 A customer s highest demand for power comes in August when it reaches 100 kw. The peak in every other month is less than 70 kw. A proposal to dim the lights for 3 hr during each of the 22 workdays in August will reduce the August peak by 10 kw. The utility s energy charge is 8 /kwh and its demand charge is $9/kW-month with an 80% ratchet on the demand charges. a) What is the current annual cost due to demand charges? b) What annual savings in demand and energy charges will result from dimming the lights? c) What is the equivalent savings expressed in /kwh? DGD - ELG

19 Example 3 (solution 1) a) At $9/kW-month, the current demand charge in August will be August = 100 kw $9/kW-month = $900 For the other 11 months, the minimum demand charge will be based on 80 kw, which is higher than the actual demand: Sept July demand charge = kw $9/kW-month 11 months = $7920 So the total annual demand charge will be Annual = $900 + $7920 = $8820 DGD - ELG

20 Example 3 (solution 2) b) By reducing the August demand by 10 kw, the annual demand charges will now be August = 90 kw $9/kW-month = $810 Sept July = kw $9/kW-month 11 month = $7128 Total annual demand charge = $810 + $7128 = $7938 Annual demand savings = $8820 $7938 = $882 August energy savings = 3 hr/day 10 kw 22 days $0.08/kWh = $52.80 Total annual savings = $882 + $52.80 = $ c) Dimming the lights saved 3 hr/day 10 kw 22 day = 660 kwh and $ or $1.42 /kwh DGD - ELG

21 Load factor Ratio of a customer s average power demand to its peak demand Useful way for utilities to characterize the cost of providing power to the customer For example, a customer with a hourly peak demand of 200 kw that uses 876,000 kwh/yr would have a load factor for 50%. 1 year = 365 days x 24 hr = 8760 hr/yr Average power = 876,000 kwh/yr / 8760 hr/yr = 100 kwh/hr DGD - ELG

22 Real-time pricing (RTP) Time-of-use (TOU) rates are crude mechanisms that attempt to capture the true cost of utility service. TOU rates use large time blocks and have only two seasons RTP on other hand offers pricing schemes as: one-day-ahead hour-by-hour real-time pricing RTP allows utilities to charge customers the true cost of energy generation and distribution. DGD - ELG

23 Questions DGD - ELG 4126