The objective of this thesis is to determine what type of expander will perform best with the ultra-low thermal energy recovery Organic Rankine Cycle (ORC). For this purpose, many types of expanders were considered, and the most promising ones were outlined. Multi-vane expander was chosen for construction. Such an expander was designed, built and tested. It was built out of materials fully compatible with the non-toxic, environmentally safe organic fluid R-245fa.