Wireless Sensor Networks (WSNs) are becoming more and more integrated into industrial and domestic systems such as transport, home automation, etc. However, due to their own characteristics, there are several issues which affect their performance. Some of the issues are briefly presented, but the emphasis is on energy constraint. Energy harvesting as one of the sources of energy in WSNs is found to be the most reliable, and this review is about energy management schemes for this source. The energy management schemes are designed for efficient use of harvested energy. The review puts the energy management schemes into classes that represent different application requirements.