Tanzania is challenged by poor energy access in rural parts of the country. Access to energy in these rural communities will require off-grid and mini-grid projects. The Tanzanian government has set a goal of establishing 1.3 million electrical connections by 2022, especially in rural areas. This would raise their connected population to about 35% from 20% in urban areas and 7% in rural ones. Tanzania’s energy goals come around the same time as the African Union (AU) and United Nations (UN) are setting goals for the continent and the world. The UN stated their goal of Sustainable Energy for All by 2030 and the AU began the Africa Renewable Energy Initiative in 2015. The African Development Bank (AfDB) has been supportive in achieving these goals. In January they approved a grant of $870,000 to support off-grid energy systems in Tanzania. Continue reading →
A captivating article published by an international team of scientists in the August issue of Nature magazine could make blue energy a powerhouse sustainable energy source in the near future. Blue energy, or osmotic power generation, refers to energy derived from the difference in salt concentration between freshwater and saltwater. At river estuaries, where river water and sea water meet, blue energy can be captured when molecules from the saltwater side move toward the freshwater side and spin a turbine.
Unfortunately, scientists have long struggled to develop a commercially viable generator with a positive return on investment. Case in point, the world’s first commercial osmotic power generator, commissioned by a Norwegian company Statkraft, could only produce enough energy to power one-tenth of one electric car battery before it was shunned in 2014. The cost? Ten years and over $100 million lost at sea. Continue reading →
Slocum et al. (2013) propose a new design for an energy storage and generation unit composed of underwater concrete spheres and offshore wind turbines. The proposed design utilizes pumped storage hydraulics (PSH). During times of low energy demand from the grid, the cylinder would contain water at equal pressure with the surrounding ocean. In the proposed design, the floating wind turbines generate energy and the excess energy is used to pump water out of the storage sphere, creating a vacuum. When energy is needed from the sphere, the turbine would open, allowing water to pass through into the sphere. The proposed sphere design would have an inside diameter of 25 m, and would retain a 1/20th-atm environment when fully discharged. The proposed design could be used without alteration in depths between 200 and 700 m, and would continue to be economically feasible to a depth of approximately 1500 m. The authors tested a small-scale dry version of the proposed design, with the test sphere having an inner chamber diameter of 75 cm, with a ten meter height difference from the top of the pump and wind turbine to the top of the sphere. The test unit was found to have a low round-trip efficiency of 11%, which the authors attribute to their inability to use the most efficient pump and turbine technology due to the small size of their test model. They calculated that in a full scale model, the lowest round-trip efficiency would be 70%. Continue reading →