Power Production from Low Temperature Heat Sources
This Master Thesis is a conclusion on work done as part of the Resource Optimization
and recovery in the Materials industry project (Roma). This project is involved in the
development of a new technology for power production from low temperature heat sources
for off gases from aluminum production cells. The technology is based on an transcritical
Rankine cycle with CO2 as a working fluid, as the work recovery circuit. The center of
the test facility is the expander, a prototype provided by Obrist Engineering . 81 tests
were perfomed to investigate the behavoir of the expander cycle. Effect of three main
parameters were investigated:
• Effect CO2 massflow rate
• Effect of heat source temperature
• Effect of CO2 condensation pressure
For each parameter combination, the high pressure side of the expander cycle was varied
in order to find the maximum power output.
This study clearly showed limitation of the turbine which cannot maintain large pressure
difference probably due to large internal leakages. As a result, turbine outlet is highly
superheated. This superheat is lost energy for the power cycle, and is simply dumped
into the heat sink. One possible improvement would be to include a recuperator that
recovers superheat after the pump.
The results also indicate that the fan of the air loop is too small: increasing the CO2 flow
rate to limit superheat at turbine outlet leads to turbine inlet temperature reduction.
Last, for large CO2 mass flow rate (3.5 kg
min) which is required for proper operation of
the turbine, the power generated is too large for the generator installed on the loop. Its
temperature reached 120 °C for some conditions. A new solution should be seeked.
Based on experimental results, a mode of the power cycle was implemented in Pro/II
and simulations were run in order to find an improved design. The main goal is to be
able to run the cycle at high CO2 mass flow rate: 3.5 kg
min. It was found that the air
loop fan should be able to deliver up to 1 260 m3
h . The new generator or braking system
should be able to absorb up to 297 W.
Place, publisher, year, edition, pages
Institutt for energi- og prosessteknikk , 2010. , 118 p.
ntnudaim:5855, MTENERG energi og miljø, Varme- og energiprosesser
IdentifiersURN: urn:nbn:no:ntnu:diva-18330Local ID: ntnudaim:5855OAI: oai:DiVA.org:ntnu-18330DiVA: diva2:565825
Eikevik, Trygve Magne, Professor