The following energy sources, in a various combinations were assessed to provide potable water using seawater reverse osmosis (SWRO) for around 50,000 people in Eritrea: wind power and solar power. Various types of SWRO technology were employed and the cost of scenarios that were able to meet the users’ water needs was compared with the costs of the equivalent diesel generator powered scenario over 25 years. The most financially-attractive scenario, a hybridised power plant using solar and wind power was compared with the equivalent conventionally (diesel generator) powered scenario using present and net present value (NPV) methodology. The discount rate used for NPV calculations was found to be pivotal for this comparison, so the logic of the appropriate discount rate was investigated and a discount rate of 3.6% was considered the most appropriate. This resulted in the renewable powered solution for this scenario being financially attractive when compared to the diesel generator powered scenario. This conclusion was mainly due to recent changes in the prices of diesel fuel in Eritrea and solar power generally. Research conducted on this scenario previously, and published in 2014 based on 2010 prices, concluded that this scenario was not financially attractive in comparison to diesel power.


  • Renewable energy is currently considered by many to only have viability for a small portion of energy delivery within a larger system due to intermittency

  • Where Pg 1 = the power available to operate the reverse osmosis (RO) plant at each hour during the year; index(i) identifies the location of the prevailing seawater temperature for each hour of the year; ppolycoeff is a file that contains all the polynomial equations relating to each 0.01°C step from 3 to 42 °C; i=1:rwr defines the number of times that the calculation should be conducted before stopping; i=the number of the calculation being conducted, in this case, conducted in sequence from 1 – the max number of which is 8760; Polyval is the matlab function that evaluates the polynomial equation identified by (index(i)) making the corresponding Pg at (i) the subject. 2.2

  • Renewable energy system employed within model The solar array for this process assumes that 10% of the available radiation, at any time when the sun is shining, is captured and converted to usable DC electrical power

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Renewable energy is currently considered by many to only have viability for a small portion of energy delivery within a larger system due to intermittency. This is in comparison to the UK, where according to the Metrological Office [2], the minimum rainfall between 1981 and 2010 is around 600 mm.

The modelling exercise
Pelton wheel
Pressure exchanger
Scenarios modelled and scaling of renewable energy scenarios
Impacts of intermittency
Reduction in solar PV price in 2016
Operations and maintenance costs
Increase in diesel fuel prices in Massawa
Price of water
Discount rate
NPV results
Overall conclusions are that

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