ENG 1102Design Project - Energy Budgets

Where is the energy going?

What resources am I using?

Agenda

● Review electrical, mechanical, and thermal energy calcs

● Introduce Energy Budgets and Applications● Show an energy budget examples● Begin planning and documenting an energy

budget for your project

Thermodynamics

● Energy may be converted from one type to another

- however -● Energy is conserved (i.e., it cannot be

created or destroyed)

Energy Sources/Resources Electrical – Power from GridChemical – Nat. Gas, Oil, SteamMechanical – Human, Potential

Sinks (Energy Consumers)Electrical – Pumps, Mill, Cooling, Gas CompressionThermal - HeatersMechanical - Drag, Rolling Resistance

Thermodynamics energy balance

BrewerySources Sinks

Electrical

Electrical

Thermal

Chemical

HPV

Sources

Sinks

HumanThermal

Potential

Potential

Mechanical

Electrical

● Flowing electrons– Metals are conductors because they contain few

loosely bound electrons in their outer shells– Electrons in the outer shells are free to jump

from one atom to the next● 1 Coulomb = 6.24150636 x 1018 electrons

(unit for counting electrons (C))

Reference: Eide, et.al, Engineering Fundamentals and Problem Solving, pg. 349 - 360

Electron Flow is Analogous to the Flow of Water in a pipe.

Flow (gpm)

Pump Valve

Pressure (psi)

Reservoir

Current(amp)

Battery Resistor

Voltage (volt)

Ground

Electron Flow is Analogous to the Flow of Water in a pipe.

No Flow

Pump Closed Valve (max resistance)

Max Pressure

Reservoir

No Current

Battery Open Switch (max resistance)

Max Voltage

Ground

Electron Flow is Analogous to the Flow of Water in a pipe.

Flow (gpm)

Pump Open Valve (full flow, min resistance)

Pressure (psi)

Reservoir

Current(amp)

Battery Closed Switch (min resistance, max flow, "short circuit")

Voltage (volt)

Ground

Terminology● Voltage (Volt, V) = potential difference,

difference in energy per unit charge, measured with a voltmeter

● Current (Amp, A) = flowrate of electrons, charge per unit time (C/s), measured with an ammeter

● Resistance (Ohm, ) = opposition to flow of charge

Electrical Power …(watts)

*

*

Power Voltage Current

P V I

* *Energy Voltage Current Time

Batteries are specified in terms of Voltage and Amp-Hours.

How much Energy is in a Battery?

What are the units?

Motor Power

• Examples:– 3 Amps, 12 Volts

P = 36 W

– 50mA, 9.4VP = 470 mW

– What's the Power? What are the units?

• Watt [=] J/sec

(3 )*(12 )

(3 / )*(12 / )

36 /

36

(50 )*(9.4 )

470

P iV

Amps Volts

C s J C

J s

Watt

P iV

mA V

P mW

As a Team

The electric motor on a table saw runs on 240V circuit and draws a current of 4.8 amps. How much power does it use?

– in watts (W)?

– in horsepower (hp)?● 1 hp = 746 W

As a Team

The electric motor on a table saw runs on 240V circuit and draws a current of 4.8 amps. How much power does it use?

– in watts (W)?

1152 W

– in horsepower (hp)?● 1 hp = 746 W

1.544hp

Electrical Power …(watts)

* *Energy Voltage Current Time

How is it sold?

Electrical Power …(watts)

* *Energy Voltage Current Time

Approx $.12 per kwatt-hour

Electrical Power

● What is Power (units?)– time rate of work or energy (V-amps, joules/sec

or watts)● How is it calculated

– P = V*I = I2*R = V2/R● How is Electrical Power (or Energy) bought

and sold (units?)– kWhr

Elevation Potential Energy …

* *Energy Mass Gravity Height

* *

EnergyAveragePower

Timeheight

AveragePower mass gravityTime

If you are peddling up a hill …

What are the units?

Thermal Power

● Heat to raise temperature of water ● Heat to evaporate water as it is held at high

temps● Other thermal power needed???

• Heat capacity (Cp) of water = 1 Btu/(lbm-deg F)• Latent Heat of evap (Hv) = 1000 Btu/lbm

– When shifting phase (liquid to gas) H = Hv

• Natural gas: – 1000 std ft^3 (scf) = 10^6 Btu– Typical unit of measure: therm=100,000 Btu– Approx cost = $1.05/therm

Reference: Holtsapple, et.al, Foundations of Engineering, pg. 71Felder & Rousseau, Elementary Principles in Chemical Processes pg. 365

Thermal Power H Cp T

Thermal Power Example

• You wish to heat a tank containing 100 lbm of water from 25°F to 50°F.

• How much energy is required (in BTU)? • How many scf of Natural Gas will you need

to purchase?

• - Cp-H2O = 1 Btu/(lbm-°F)

• - 1000 std ft^3 (scf) = 10^6 Btu

H Cp T

25

25 *100

2500 2.5

1( ) * (25 )

BtuH

lbm

BtuE lbm

lbm

E Btu scf

H Cp T

BtuH F

lbmF

Thermal Power Example• Mass of Water = 100 lbm of

water• T = 25°F to 50°F = 25°F• How much energy is

required (in BTU)? • How many scf of Natural

Gas will you need to purchase?

• - Cp-H2O = 1 Btu/(lbm-°F)

• - 1000 std ft^3 (scf) = 10^6 Btu

● Lance Armstrong: approx 500W over 1 hr– Approx. 1kW over 1 minute

● Bike Rider Guy/Gal: approx 100-200W over 1 hr– Approx. 400W over 1 minute

Power = Energy/Time

Reference: Wilson, et.al, Bicycle Science, pg. 44

Human Power

Resource Budget: Accounting for Materials

● Tracks all inputs and outputs to your process (energy, raw materials, byproducts, products, etc.)

● Estimates energy and materials consumed in process

● Used to estimate annual costs/profits of company

● Used to identify opportunities for process improvement

What is an Energy Budget?

● ????

What is an Energy Budget?

● A means of planning the energy usage of a system

● A means of cost predictions and control● An engineering tool to optimize the efficiency

of any energy using system● A “balance sheet” of energy sources and

sinks

What are the major energy consumers? (Sinks)

Where does the energy come from? (Sources)

Residential Homes and Commercial Buildings

Configuration Diagram Brewery

Where are…

Sources?

Sinks?

Energy Budget - BrewingPurpose(s):

– To estimate the energy cost for one batch of beer● In a spreadsheet, list unit operations and estimate

power requirement for the line and annual cost to operate line.

● Cite references and state your assumptions in your spreadsheet

Energy Budget – Flood Control

Purpose(s): - To estimate the energy cost for pumping station at

“rest,” at full operation and expected annual use

- Document assumptions in a spreadsheet that clearly shows units and calculations

● Cite references

Example Energy Budget – Brewery(Flood will be similar, electrical)

Energy Budget – HPV

Purpose(s): - To estimate the HPV speed for a given set of

conditions

- Document assumptions in a spreadsheet that clearly shows units and calculations

● Cite references

Material Budget● Purpose(s):

– (Brew) To complete a mass balance on a typical brewing line and calculate the input/output quantities

– (Flood) To determine the amount (and type) of material used in constructing flood control system

– AND…To determine the amount of time necessary to construct your flood control system (will it be ready for next hurricane season?)

● Can be completed in spreadsheet format.● Cite references and state your assumptions

Brewery Mass Balance

16 barrels

?

?

???

??

??

?

?

?

General Process Info – What changes are you planning?

Deliverable 6 - Resource BudgetDue Week 10, Day 1

Summarize your Energy and Material Budgets / Mass Balance findings in a memo

●Discuss … how does this estimate compare with your design criteria?

●Suggest a way to significantly reduce energy usage.

Refer to RFP for your project.