Battery boat

Abstract

Developments in the field of renewable energy technologies have lead to low energy cost in areas with specific characteristics. In the Middle East solar power plants are built for prices around 3 cent per kilowatt-hour and bids below 3 cent have been placed. In Europe wind energy is the second largest source of renewable energy after biomass. Although, wind farms are being built without subsidy the total cost of a wind farm is much higher in the order of 14 cent per kWh and it can decrease to 10 cent by 2030.

In this research an concept study for the transport of electric energy is made to find an answer to the question: “is it possible to ship electric energy which is delivered in a port between areas of generation and consumption over a fixed distance with the use of a ship and deliver it for a levelised cost of electricity (LCoE) which is competitive in the market of unloading.”

The cost of a kilowatt-hour of electric energy in the Dutch market is 8.33 if it is produced by a modern gas fired power plant and if the cost for CO2 emissions are included according to the current prices in the European emission trading scheme. If higher carbon cost scenario's are applied the price could increase to prices over 17 cent per kilowatt-hour. The concepts in this study are tested against four different carbon emission cost scenario's ranging from 8 euro/tCO2 to 190 euro/tCO2

Most electrical energy is transported by electric energy power grids. For long distance high volume energy transmission a high voltage direct current energy cable is the most efficient way to transport energy but at larger distances the transmission system gets more expensive. In this research the electric cable is used as a reference case which the concept has to outperform.

To test the concepts a non-linear model is made which is solved with Matlab-integrated solvers to find the optimal transport concept. The model works by optimising the main dimensions of the ship. With this optimal ship design concepts are analysed. For this research: a concept based on a hydrogen-carrier (ammonia) and a concept based on thermal energy storage are discussed.
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The hydrogen-carrier concept uses ammonia as a carrier. Ammonia has a high energy content and can be produced with the Haber Bosch process or with Solid State Ammonia Synthesis (SSAS). If the energy is produced using the well known Haber-Bosch process in 2018 the levelised cost of energy is 21.2 and 24.2 cent per kilowatt hour depending on the distance. Developments in the field of electrolysers will reduce the capital investment which can reduce the price to 17.8 to 20.8 cent per kilowatt hour by 2025 if the energy is supplied at 2 cent per kilowatt hour to the ammonia production facility.

The SSAS method offers higher energy effincies at lower capital investment cost. The LCOE calculated in this research is 11.4 to 16.4 cent per kilowatt-hour.
The thermal energy storage concept is based on molten salt. Molten salt is being used in concentrated solar power plants as a storage of energy. In the concept used in this project the molten salt is transported to another part where the heat which is stored in the salt is used to generate electricity. The LCoE is already 28.5 cent per kilowatt-hour at a distance of 1,000 nm. The thermal energy storage concept is more expensive than the ammonia concept.

Depending on the distance and the carbon cost scenario's the concept can be competitive to the fixed connection with a cable and fossil fired power plants in the home market. If the low cost carbon scenario's (1 and 2) are applied by law makers the concept of electrical energy by sea is not competitive but if politicians would decide to increase the cost for carbon emissions the transport could become competitive. When the carbon emission cost increase to values over 100 euro/tCO2 the SSAS concept is competitive for distance up to 2,000 nm but it still more expensive than a cable connection. For this distances larger than 4,000 nm and carbon prices according to the 4th scenario (190 euro/tCO2) the SSAS-based concept can be a competitive energy supplier.