Towards implementation of reverse electrodialysis for power generation from salinity gradients

Abstract

ab s t r ac tReverse electrodialysis is a conversion technique to obtain electricity from salinity gradients. Over the past few years, the performance of reverse electrodialysis on laboratory scale has improved considerably. In this paper, we discuss the challenges we are still facing concerning the economic and technological feasibility and the developing path of reverse electrodialysis. We focus on the following issues: (i) the development of low-cost membranes, (ii) pre-treatment in relation to stack design and operation, and (iii) the economics of reverse electrodialysis. For membranes, the challenge is to increase availability (>km 2 /y) at reduced cost (<2 €/m 2 ). The membranes should be manufactured at high speed to meet this challenge. For pre-treatment, a capital-extensive microscreen filter with 50 μm pores was selected and tested. Such a straightforward pre-treatment is only sufficient given the fact that the reverse electrodialysis stack was redesigned towards a more robust spacer-free system. For the economic feasibility, a 200 kW repetitive unit was designed. The cost price is estimated to be less than 0.08 €/kWh (excluding any subsidy or compensation), comparable with that of wind energy. The feasibility of the technology should be proved with a scaled-up system under practical conditions. The intended pilot facility at the Afsluitdijk (The Netherlands) will be an essential step towards implementation of reverse electrodialysis for power generation.

A new reverse electrodialysis design strategy which significantly reduces the levelized cost of electricity

“…The pretreatment system is based on a setup suggested by Post et al [17]. It consists of coarse mediafiltration in the form of two rotating drum filters, with light chlorination (1 ppm).…”

“…We assume a plant life of 20 years (Γ in periods) and an annualized cost of capital r of 6% [17]. The net present value consists of a capital contribution for the RED stack and a capital contribution for the pretreatment system.…”

“…We use a capital cost figure for the pretreatment system K PT of 20 $/(m 3 /day), which includes operating costs. The capital cost of the pretreatment system is computed by dividing the total construction costs by the operating flux of the system developed by Post et al [17]. The chemical cost figure associated with light chlorination is 0.33 $/kg [19].…”

“…A summary of the model parameters and properties is provided in Table E [17,19] a Represents the average of the measured head losses by Post et al [17] in the summer, winter, and spring…”

Membrane Operations for Process Intensification in Desalination

“…The power generated is termed as blue energy or salinity gradient power. The total global potential of blue energy has been estimated to be about 1.4-2.6 TW out of which ~980 GW is extractable depending on the technology applied [25]. It has been demonstrated that salinity gradient energy is able to fulfil 20% of the current global energy demand.…”