Heat pipes thermoelectric solar collectors for energy applications Gunay Omer a , Abdullah Hakan Yavuz b,* , Rasit Ahiska c a TES Ltd Co., Ankara, Turkey b Faculty of Engineering and Natural Sciences, Gaziosmanpasa University, Tokat, Turkey c Department of Physics, Faculty of Science, Gazi University, Ankara, Turkey article info Article history: Received 29 October 2016 Received in revised form 6 January 2017 Accepted 23 January 2017 Available online xxx Keywords: Thermoelectric Heat pipe Solar collector Renewable energy Efficiency abstract This study investigates the load characteristics of heat pipe thermoelectric solar collector (HPTSC) in practice. Heat pipe thermoelectric solar collector converts the heat generated by the Sun directly into electrical energy and produces hot water as well. The maximum power in HPTSC is obtained when the internal resistance of the thermoelectric module is equal to the load resistance. It has been observed to be possible to produce both hot water and electricity by improving available solar collectors or producing new generation HPTSC. While it is possible to generate an electrical power of 160 W from a HPTSC of one square meter using the thermoelectric method, the power produced with an average photovoltaic panel with the same area is only 132 W. Accordingly, HPTSC is a superior alternative not only to available solar collectors, but also to available PV panels. HPTSC, involving three different technologies, is environmentally friendly and certainly a product that allows for more efficient use of solar energy. © 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Introduction In parallel with rapidly increasing population growth and industrialization increase the need for energy in the world and the vast majority of the energy used is generated from fossil fuels, which are harmful to the environment. Fossil fuel-based energy use causes considerable negativities such as foreign- source dependency, high import expenses and environ- mental issues and together with the depletion of world fossil fuel reserves, these negativities increase the importance of renewable energy sources. The Sun, the source of all energy sources is the cleanest type of energy. The two main effects of the solar energy are the thermal effect and the radiation effect. The radiation effect is converted to electrical energy via photovoltaic panels, whereas the thermal energy is converted to electrical energy using the thermoelectric method. Although photovoltaic panels are widely used in today's world, it is not possible to mention the use of thermoelectric solar panels. However, solar heat is widely used to heat water with solar collectors. Solar collectors are produced in many countries including Turkey and used to produce hot water. Solar collectors are available in many different models, powers and capacities [1,2]. However, only a small fracture of the heat collected by solar collectors is used to heat water. 60% of solar heat is discharged to the environment, which leads to pollution [3,4]. On the other hand, thermoelectric generator systems do not passes moving parts, have a simple structure, do not require maintenance, are durable, allow for temperature control, * Corresponding author. E-mail addresses: gunayomer84@gmail.com (G. Omer), hakan.yavuz@gop.edu.tr (A.H. Yavuz), rasitahiska@gmail.com (R. Ahiska). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2017) 1 e4 http://dx.doi.org/10.1016/j.ijhydene.2017.01.132 0360-3199/© 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Omer G, et al., Heat pipes thermoelectric solar collectors for energy applications, International Journal of Hydrogen Energy (2017), http://dx.doi.org/10.1016/j.ijhydene.2017.01.132