Beginning Question 1.How much wood would a woodchuck chuck if a woodchuck could chuck wood? A.A lot B.A little C.None D.Don’t know

Admin I sent a test message yesterday If you didn’t get it: Send me an message with ARE346N in the subject line If you change your address over the course of the semester you are responsible for forwarding me your new address

Admin Textbook 3 rd edition of Tao and Janis is on order at the co-op Only 5 copies were ordered, so let them know if more or you want them

Objectives Critically analyze conservation claims Introduction to course themes List and define terms associated with electrical design in buildings Calculate electric quantities with Ohm’s Law and Kirchov’s Law (review) Calculate electricity costs for residential and commercial buildings Major emphasis – how do you begin designing an electrical system?

Critical Analysis Central objective of this course Myths website – myths aren’t always false Goal is to evaluate them Project I

2) Myth 1: How long would the average American have to leave the bathroom tap running to use as much water as one shower A.60 minutes B.30 minutes C.15 minutes D.5 minutes

3) How long is your average shower? A.2 minutes B.5 minutes C.10 minutes D.20 minutes E.30 minutes

Myth 1: Tight With the Tap Claim is unlikely to be true because very few people leave their taps running for ½ hour.

4) Myth 2: Using drapes reduces heat loss by ~1/3 for single glazed windows. A.Untrue, heat loss is unaffected by drapes B.Untrue, heat loss is only reduced by 10–15% C.Approximately true D.Untrue, a drape reduces heat loss by more than 40%

Conclusions Claims are often made without verification We have the tools to evaluate these claims Critical analysis is necessary/important for engineering Law of unintended consequences

Where are we going? Electrical systems Lighting technology and design

Applied Electrical Concepts Use terms to describe building electrical system AC vs DCch. 9 Ohm’s and Kirchov’s Lawsch. 8 Power vs. Energych. 9 Inductors and Capacitors Power Factorch. 9 Single-phase vs. Three-phasech. 9 Groundingch. 9

Electrical Codes National Electrical Code (NEC aka NFPA 70) Library website Focus on safety Talk to the electrical inspector

AC DC Direct Current (DC) Sign matters Alternating Current (AC) Switching polarity Which are the following? Photovoltaic solar cell Automobile alternator Household outlet Outlet in ECJ Battery High voltage lines

AC terms Frequency, f [Hz] Wall outlet? Fluorescent light? Clock? Electric resistance heater? Capacitor (plates separated by dielectric) Inductor(coil of wire) Transformers

Why use AC? Easier to generate Able to use inductors and capacitors in meaningful way Voltage changes much easier Lower distribution losses

Across a transformer I 1 E 1 = I 2 E 2 Voltage and Current Voltage (potential difference) Units? Symbol V or E Current (electron flow) Units? Symbol I

Ref: Tao and Janis (2001)

Ohm’s and Kirchov’s Laws V = IR, E = IR (E = energy [V]) P = EI = I 2 R ∑I = 0 for a node ∑E = 0 for a closed loop Are these for AC or DC or both?

Single-Phase vs. Three-Phase Ref: Tao and Janis (2001) For three phase: P=√3 E I

5) Why do commercial buildings use 3  power? a)Requires fewer wires b)Higher motor efficiency c)Requires bigger wires d)Smaller space requirements

Why Three-Phase? Larger loads Smaller wire sizes (because higher voltages) P = I 2 R More efficient use of neutral wire 3  needed for efficient operation of equipment

Power Factor Difference between power supplied and power that does useful work “working power” P=E I cos θ θ is the phase difference between current and voltage For three phase P=√3 E I cos θ Commercial buildings pay for power factor.

6) Are kWh units of energy or power? A.Energy B.Power

Electricity Billing (ch. 13) Electrical Use (energy) Peak Demand (power) Power factor Which is largest portion of residential bill? What about for commercial buildings? ates/Commercial/index.htmhttp:// ates/Commercial/index.htm

Example: September cost of Electricity for ECJ Assume ECJ is 120,000 ft2 and that it needs, on average, 8 W/ft 2 for 8 hours a day, 6 W/ W/ft 2 for 4 hours a day, and 4 W/ft 2 for 12 hours a day Use Austin Energy Large Primary summer service rate 1.5¢/kWh, $/peak kW/month Assume no power factor charges

7) What is peak demand? A kW/ft 2 × 120,000 ft 2 = 2,160 kW B kW/ft 2 × 120,000 ft 2 = 960 kW C kW/ft 2 × 120,000 ft 2 × 8 hr = 17,280 kWh D kW/ft 2 × 120,000 ft 2 × 30 days = 28,800 kW

Solution large primary service $/kW $/kWh Daily $ $ hourskWkWh demand $12, energy $ 7, TOTAL16320 Total $19,440.00

Other Pricing Strategies Time of use pricing Becoming more common for residential and commercial Electricity cost related to actual cost Requires meter Interruptible pricing Utility can shut off electricity for periods of time

Summary Know where to find NEC Compare DC and AC Calculate current/voltage across a transformer Describe 3-phase power and compare to 1- phase List reasons for using 3-phase List and explain components of electrical billing Calculate commercial electricity bill