Fall 201208.28.2012ENERGY MANAGEMENTLecture 2--1 Lecture 2 BrieflySolar and Wave Energy (GREEN) Book chapter 5Boilers and Fired Systems Book Chapter 6Steam.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--1

Lecture 2

Briefly—Solar and Wave Energy (GREEN) Book chapter 5—Boilers and Fired Systems

Book Chapter 6—Steam and Condensate Systems

Introduction to solar and wind energy• This section includes discussions of renewable

energy resources, but primarily those of solar and wind.

• At the present time the payback period is greater than other renewable's. However, as time proceeds the payback period will decrease.

• The payback will gradually approach the other types of energy and storage systems

Fall 2012—08.28.12 ENERGY MANAGEMENT Lecture 2--2

ULL Ocean Energy & Technology Team

• Dr. Ted Kozman

• Dr. Yucheng Liu

• Jeremiah Pastor– Team Leader

• Kelly Guiberteau

• Grant Caliver

• Raul Viera

• Clay Guillory

• Kevin Judice

Comparison to Other Estimates

EPRI used spectral analysis to estimate60 TWh/yr on inner shelf80 TWh/yr on outer shelf

Extrapolation methods were not givenUsed 4 buoys

Further offshore2005-2009

2005 had a high number of eventsMore events offshore

Classified GOM as “Mildly Energetic” (< 10 kW/m)

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--5

Why the GOMHigh Activity

4,125 platforms2,380 companies161 operators561Gm2 leases

Ship Diesel to platformsFuel cost Shipping costEmissions cost

Permit growth is spreading to deep waters.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--7

Spring 2010—01.21.10 ENERGY MANAGEMENT Lecture 2--8

Spring 2010—01.21.10 ENERGY MANAGEMENT Lecture 2--10

Power Buoy

Ocean Power Technology, US and UKPoint Absorber44 m tall, 11 m diameter8 km offshore20 – 50 kW per unit Multiple unitsCommercial unit in Spain 1.39 MW

EnergeTech

AustraliaOscillating Water

Column35 meters wide450 tons $2-3 Million Up to 50 meters

offshoreDouble acting turbine

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--13

Ideas for fuel-fired systems

• Almost two-thirds of the fossil-fuel energy consumed in the United States involves the use of a boiler, furnace, or other fired system. Over 68% of the electricity generated in the United States is produced through the combustion of coal, fuel oil, and natural gas.

• Boilers and fired systems or subsystems are not inherently energy efficient—with these systems there is significant opportunities for reducing energy consumption.

• Indeed, in operating the IAC for the first year, only 13% of the plants could have improved efficiency in their fossil-fuel fired systems but saved more than 80% of the energy recommendations (in MMBTU)

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--14

Analysis of boilers and fired systems

• Governing equations– Not easy—because all values may change with

time.

• Heat and mass balances are used to determine where all the heat or mass enters or leaves a system.

dt cost) (fuel * ncy)(1/efficie * (load) cost Energy

dt ncy)(1/efficie * (load) nconsumptio Energy

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--15

Key elements for maximum efficiency

• Percent increase in efficiency or fuel savings = [(new eff.) – (old eff.)]/(new eff.)

• Ensure the furnace walls and stack vent are airtight and not a source of air infiltration.

• Ensure optimum burner performance• Establish a maintenance program and establish an

operator’s log and monitor key parameters. (Make corrections to operations if the key parameters change significantly.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--16

Exhaust Stack Temperature

• We need to reject stack gases at the lowest possible temperature consistent with design principles -- use additional heat recovery methods if the flue-gas temperature exceeds 250oF.

• Excess heat can be recovered by adding an economizer to heat the the inlet (makeup) water—should be Tw = Tg –100oF or adding a gas/air pre-heater to heat the intake air.

• For units with stack gas in the >1,000oF, use an additional unit to generate steam or other medium

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--17

Requirements for maximum economy

• Boilers generally operate most efficiently at 65% to 85% full-load rating. Centrifugal fans (with motors) at 80% to 90%. Efficiencies fall off at higher or lower load points.

• It is usually more efficient to operate a lesser number of boilers at higher loads than larger number at low loads.

• Boilers should be put into service in order of decreasing efficiency starting with the most efficient unit.

• Newer units and units with higher capacity are generally more efficient than older, smaller units.

• Generally, steam plant load swings should be taken in the smallest and least efficient unit.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--18

Fuel Considerations• Natural Gas:

– Costs have been artificially low (up until recently) by government control.– Only limited equipment is necessary.– Boiler costs are less because of heat transfer and flame characteristics.– Little or no pollution control equipment is required.

• Fuel Oil:– Many classifications and makeup of oils– All fuel oil has a high heat value (HHV) and a low heat value (LHV). LHV is the heat

produced during combustion but HHV is used in the US.– Viscosity can vary depending on the oil, the higher the viscosity the operation and design are

more difficult.– Flash points are normally high, so fuel oils are relatively safe to handle.– Pour point—determines if storage heating is required in colder climates.– Sulfur content is an important consideration in meeting environmental regulations.– Ash and other contaminates can cause reduced heat transfer and lower efficiency.

• Coal:– Environmental limitations, higher capital costs, larger storage requirements, higher

maintenance costs and increasing transportation costs.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--19

Steam and Condensate Systems

• Energy conservation opportunities:

– General operations:

• Review operation of long steam lines

• Review operation of steams systems for occasional services.

• Implement regular steam leak survey.

• Monitor steam use.

• Reduce temperature requirements of heated storage vessels to the absolute minimum.

– Steam trapping:

• Check sizing and institute regular survey and maintenance program.

– Condensate recovery:

• Survey condensate sources presently discharged to waste drains

• Consider pressurizing atmospheric condensate to minimize flash losses.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--20

Continued

• Energy conservation opportunities (continued)

– Mechanical drive turbines:

• Consider shutting down standby turbines.

• Clean turbines on a regular basis

• Consider CHP instead of large pressure-reducing valves.

– Insulation:• Use infrared thermography to locate areas insulation deterioration of piping

and equipment on a regular basis.

• Re-evaluate insulating previously uninsulated equipment.

• Survey the economics of retrofitting additional insulation on insulated equipment.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--21

Steam properties and definitions

• British Thermal Unit (Btu)—amount of heat required to raise 1 pound of water 1 degree Fahrenheit.

• Boiling point—the temperature at which water begins to boil at any given pressure.

• Saturated and superheated steam—saturated temperature at a pressure will produce more steam and doesn’t raise the temperature as more heat is added. If all water is boiled off—and we continue to add heat and the temperature continues to rise this is called superheated steam.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--22

Boiler Blow down

• In steam generation using boilers, most water impurities are not evaporated with the steam and thus concentrate in the boiler water. The concentration of the impurities is usually regulated by the adjustment of the continuous blow down valve, which controls the amount of water (and impurities) purged from the steam drum.

• Too little blowdown, sludge deposits and carryover will result.

• Too much blowdown, excessive hot water is removed, resulting in increased boiler fuel requirements and inefficiencies.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--23

Energy Conservation Opportunities:

• General Operations:– Regular steam leak survey and repair.– Plant-wide steam balance to eliminate venting low-pressure

steam

• Steam Trapping:– Regular survey and maintenance program.– Check sizing periodically.

• Insulation:– Survey and maintain on a regular basis– Review insulation economics of all uninsulated areas on a

periodic basis.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--24

Definitions

• Sensible Heat– Heat input that can be “sensed” as in raising the

temperature

• Latent Heat– Heat that goes into a process and converts it from liquid

to vapor

• Enthalpy– Total energy content of a flowing medium (usually

expressed in Btu/lb) takes both latent and sensible heat into account

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--25

Steam Traps

• May represent a major energy conservation opportunity (or problem). Basic function of a steam trap is to allow condensate formed in the heating process to be drained from the the equipment. Inefficient condensate removal almost always increases the amount of energy required by the process and may produce water hammer (can cause equipment damage).

• Steam traps may also facilitate the removal of air from the steam space. The presence of air in the system reduces the temperature for heat transfer.

• Steam traps are sized in two specifications: condensate load (#/hr or gal/min) and the pressure differential across the trap (psig). It is a good idea to size the trap with a know load and a factor of safety (usually 3 or 4).

• Steam traps can either fail open (allowing live steam to discharge) or closed (causing condensate to back up into the steam system—may lead to disastrous effects). Typically 15% to 60% of the traps in a system may be blowing through, wasting enormous amounts of steam and energy.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--26

HW 2—Problems: 1-4Due by 9/04/2012, 1pm

• At design parameters, what should be the O2 content in the stack for a gas-fired boiler?

• All else being equal, what kind of combustion efficiency gains might be obtained by lowering the stack temperature rise from 450oF to 250oF?

• All else being equal, what kind of combustion efficiency gains might be obtained by lowering the stack O2 content from 9% to 2%?

• Develop a spreadsheet that calculates boiler efficiency based upon stack temperature rise and O2 content.

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--27

HW2—Problem 5

• Setup a saving operation by running two boilers instead of three similar to that shown on pages 102-105:– Boiler 1: 140,000 #/hr., 186 BTU/hr.?– Boiler 2: 140,000 #/hr., 204 BTU/hr.?– Boiler 3: 70,000 #/hr., 100 BTU/hr. ?

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--28

HW2—Problem 6

• 500-ft of 6-in. steam pipe carries saturated steam at 150 psig. Tables obtained from an insulation manufacturer indicate a heat loss from this piping run is presently 500,000 Btu/hr. With proper insulation, the manufacturer’s tables indicate that this loss could be reduced to 5000 Btu/hr. With the boiler at 85% efficiency, what is the steam savings and the fuel savings?

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--29

HW2—Problems 7, 8

• Estimate the steam usage and fuel usage of a of a paper corrugator doing 100,000 ft2 per hour. The efficiency of the current steam boiler is 75%.

• Estimate the steam usage and fuel usage of a 25 ft steam table in restaurant usage. The efficiency of the steam boiler is 80%

Fall 2012—08.28.2012 ENERGY MANAGEMENT Lecture 2--30

HW2—Problem 9, 10

• What is the annual cost of a 1/16 inch diameter steam leak in a system operating at 250 psi with the normal cost of steam at $3.50/1000 lbs.?

• What things (and how) are to be inspected during routine maintenance of a steam system. Estimate potential savings by fixing suck things as traps and leaks.