Oceanic Thermal Energy Oceanic Thermal Energy ConversionsConversions

Group Members:Group Members:Brooks CollinsBrooks Collins

Kirby LittleKirby LittleChris PetysChris PetysCraig TestaCraig Testa

Background InformationBackground Information• OTEC system is OTEC system is

based on the based on the Rankine CycleRankine Cycle

• Uses the vertical Uses the vertical temperature temperature gradient in the gradient in the ocean as a heat ocean as a heat sink/sourcesink/source

• Mainly used in Mainly used in equatorial waters equatorial waters where temperature where temperature gradient is greatestgradient is greatest

Closed Rankine Cycle Closed Rankine Cycle OverviewOverview

• 1-2 Power in to 1-2 Power in to pressurize liquid to pressurize liquid to higher pressurehigher pressure

• 2-3 Heat addition 2-3 Heat addition to evaporate to evaporate ammoniaammonia

• 3-4 Work produced 3-4 Work produced from expansion from expansion through turbinethrough turbine

• 4-1 Heat extraction 4-1 Heat extraction to condense the to condense the ammonia before ammonia before pumppump

ClosedClosedRankine Cycle CalculationsRankine Cycle Calculations

wpump h2 h1 P2 P1

carnot 1TLTH

qevaporator h3 h2

wturbine h3 h4 rankine 1qoutqin

qcondenser h4 h1

Pros of OTECPros of OTEC• Extremely benign impact on Extremely benign impact on

environmentenvironment• No dependency on oilNo dependency on oil• Minimal maintenance costs compared to Minimal maintenance costs compared to

conventional power production plantsconventional power production plants• Open cycle OTEC systems can produce Open cycle OTEC systems can produce

desalinated water which is very desalinated water which is very important in third-world countriesimportant in third-world countries

Cons of OTECCons of OTEC• Low thermal efficiency due to small temperature Low thermal efficiency due to small temperature

gradient between heat sink and sourcegradient between heat sink and source• OTEC technology is only ideally suitable in OTEC technology is only ideally suitable in

equatorial watersequatorial waters• Only moderate power outputs are availableOnly moderate power outputs are available• Currently this technology is not as monetarily Currently this technology is not as monetarily

feasible as conventional power production feasible as conventional power production plantsplants

• The manufacturing and installation of the The manufacturing and installation of the extremely long cold water pipes is extremely extremely long cold water pipes is extremely time consuming and costly. time consuming and costly.

Problem StatementProblem Statement• To create and design an operating Oceanic Thermal To create and design an operating Oceanic Thermal

Energy Conversion model that employs a closed Energy Conversion model that employs a closed Rankine Cycle that utilizes ammonia as the working Rankine Cycle that utilizes ammonia as the working fluid to illustrate the viability of OTEC power production. fluid to illustrate the viability of OTEC power production.

SpecificationsSpecifications• Produce 100 Watts of power Produce 100 Watts of power • Be smaller than 8 ft. wide, 6 ft. tall, and 2 Be smaller than 8 ft. wide, 6 ft. tall, and 2

ft. deep. ft. deep. • Final product must be easily portable. Final product must be easily portable. • OTEC model must be aesthetically OTEC model must be aesthetically

pleasing and allow viewers to easily pleasing and allow viewers to easily understand and view the inner-workings of understand and view the inner-workings of the Rankine Cycle utilized by OTEC the Rankine Cycle utilized by OTEC systems. systems.

• Must start and stop operation using simple Must start and stop operation using simple mechanical or electrical devicesmechanical or electrical devices

• Must not endanger the operator or anyone Must not endanger the operator or anyone viewing the OTEC presentationviewing the OTEC presentation

Heat Pump ConversionHeat Pump Conversion• One possible design idea is to convert a heat One possible design idea is to convert a heat

pump into a power producing Rankine Cyclepump into a power producing Rankine Cycle• Many moderately sized Geothermal energy Many moderately sized Geothermal energy

cycles use large commercially available AC units. cycles use large commercially available AC units. • Objective is to make the compressor function as Objective is to make the compressor function as

a turbine/generator a turbine/generator • Add an auxiliary pump to circulate and Add an auxiliary pump to circulate and

pressurize the working fluid throughout the cyclepressurize the working fluid throughout the cycle• Very little modification is necessary to convert Very little modification is necessary to convert

heat pumps and AC units into power producing heat pumps and AC units into power producing unitsunits

Future CalendarFuture Calendar

Future Design PlansFuture Design Plans• Research Heat Pump Research Heat Pump

Conversion Conversion • Find pump that fits Find pump that fits

mass flow rate and mass flow rate and pressure specificationspressure specifications

• Determine whether Determine whether shell and tube or plate shell and tube or plate and frame heat and frame heat exchanger will be more exchanger will be more efficient efficient

• Select piping sizes Select piping sizes based on calculationsbased on calculations

• Find optimal size of Find optimal size of heat exchangers for heat exchangers for effective heat transfer effective heat transfer between the ammonia between the ammonia and the heat and the heat sink/sourcessink/sources