Research Projects and Publications

Small Scale Electricity Production From Low Temperature Geothermal Resources Using Organic Rankine Cycle

Geothermal Engineering and Exploration Show all

Author: Emilía Valdimarsdóttir

Year: 2017

Supervisors: María Sigríður Guðjónsdóttir & Jón Matthíasson


The most common use of geothermal energy for electricity production is by using the fluid in it's vapor state. Low temperature geothermal sources in liquid form are, in many areas in Iceland, used for district heating. Another possible utilization of the low temperature geothermal resource is to generate electricity by the use of binary cycles. Binary cycles are well known throughout the world and the most common cycle is the Organic Rankine Cycle (ORC). The ORC uses a low temperature geothermal resource to heat up a working fluid, that has a lower boiling point than water. The objective of this study was to model an ORC unit in Engineering Equation Solver (EES) in order to produce 100 kW of electricity for a small scale user such as a greenhouse. The motivation for this thesis was an existing ORC unit that was built by XRG Power and the Innovation Center in 2015. That unit produces 1 kW and this model's main focus was to scale that power output up to 100 kW, and find out whether that unit would be a feasible investment for greenhouse owners. A model was made in EES and components of the ORC explained. A working fluid comparison study was performed and the working fluid R1234yf was chosen as the best option based on given assumptions. An economic feasibility study was performed and it was concluded that this 100 kW ORC unit is an investment worth making for greenhouse owners. A case study was performed for an Icelandic greenhouse and, even though the model delivered less than the model's ambition, it was concluded that the unit would be a good investment for that greenhouse. A comparison was made with the XRG unit and different parameters tested. This study provides a basis for continuing research of this subject.

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