Personal electronic devices such as mobile/cell phones, radios and wireless sensors traditionally depend on energy
storage technologies, such as batteries, for operation. By harvesting energy from the local environment, these devices can
achieve greater run-times without the need for battery recharging or replacement. Harvesting energy could also achieve a
reduction in the weight and volume of the personal devices - as batteries often make up more than half the
weight/volume of these devices. Motion energy harvesting is one such approach where energy from mechanical motion
can be converted into electrical energy. This can be achieved through the use of flexible piezoelectric transducer
materials such as polyvinylidene fluoride (PVDF). A problem with these transducer materials it that their behaviour is
non-linear due to operating and environmental conditions. Hence, for this reason researchers have found it has been
difficult to measure the harvesting performance i.e. mechanical-to-electrical conversion efficiency. At CSIRO we are
currently evaluating the performance of flexible transducers for use as motion energy harvesters. Preliminary results
suggest an overall energy harvesting conversion efficiency of 0.65% for a flexible transducer material.
Over the last decade, wireless computing and mobile devices have decreased in size and power requirements. These
devices traditionally have power requirements that necessitate the need for batteries as a power source. As the power
requirements reduce, alternative means of power become available. One of these is the use of thermal energy. The use of
thermal energy requires a high temperature source and a lower temperature sink. Energy is extracted as heat flows from
the hot side to the cold side. The magnitude of the heat source is not as critical as the magnitude of the temperature
difference between the source and sink. One source of temperature difference is that between a body of water and a solar
heated object. A device has been designed and tested to capture thermoelectric energy where one side of the device is
immersed in water. The other side is exposed to solar radiation. Typically, during the day this is warmer than the water.
However, at night this situation is reversed. This paper discusses the design and manufacture of an innovative thermal
energy capturing device. This device was used to capture energy across an air water boundary. Theoretical estimations of
power available from measured temperature differences are compared with the results of the designed device.
Seventy percent of the Earth's surface is covered by water and all living things are dependent upon this resource. As
such there are many applications for monitoring environmental data in and around aquatic environments. Wireless sensor
networks are poised to revolutionise this process as the reduction in size and power consumption of electronics are
opening up many new possibilities for these networks. Aquatic sensor nodes are usually battery powered, so as sensor
networks increase in number and size, replacement of depleted batteries becomes time consuming, wasteful and in some
cases unfeasible. Additionally, a battery that is large enough to last the life of a sensor node would dominate the overall
size of the node, and thus would not be very attractive or practical. As a result, there is a clear need to explore novel
alternatives to power sensor nodes/networks, as existing battery technology hinders the widespread deployment of these
networks. By harvesting energy from their local environment, sensor networks can achieve much greater run-times, years
not months, with potentially lower cost and weight. A potential renewable energy source in aquatic environments exists
via the temperature gradient present between the water layer and ambient air. A body of water will be either a few
degrees warmer or colder than the air directly above it dependant on its latitude, time of year and time of day. By
incorporating a thermal energy harvesting device into the sensor node deployment which promotes the flow of heat
energy across the thermal gradient, a portion of the energy flow can be converted into useable power for the sensor node.
To further increase this temperature difference during the day the top section can be heated to temperatures above the
ambient air temperature by absorbing the incoming sunlight. As an initial exploration into the potential of this novel
power source we have developed a model of the process. By inputting environmental data, the model calculates the
power which can be extracted by a thermal energy harvesting device. Initial outputs show a possibility of up to 10W/m2
of power available from measured sites assuming a thermal energy harvester operating with Carnot efficiency.