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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Brendon Harkness

Sustainable Pumping Options for Global Refugee Camp Water Supplies

We face an uncertain future. The impact of population growth, a changing society, climate events, and rising instances of significant and protracted conflict sets a challenging scene for sustainable humanitarian assistance. In tension with these
disturbing trends is a need to reduce global per capita energy use, and to decarbonise its generation, and this can appear to intensify the challenge. However, in many of today's conOict 'hotspots', considerable levels of solar irradiation are available.

Solar PV water pumping is a mature technology and has been trialled in a number of refugee camps, particularly in sub-Saharan Afr:ca, where fuel transport can be expensive and security risk is often high. However, the value of energy in tllis context is not well understood, and requires a new framework to understand both the impact and benefits of energy utilisation.

This research has sought firstly to reconcile th e energy generation profile of solar PV and diesel electricity generation with the delivery of water supply se rvices; secondly, to value the utilisation of energy in support of wider opportUJlities witl1in refugee camps and finally, to develop a model to support investment decisions by incorporating technical, economic, environmental, social and management considerations.

A case study of a recent solar PV installation at Nyarugusu refugee camp in Tanzania was analysed, and this initiated the cevelopment of an innovative net energy model (NEMa) that incorporates a proposed assessment ft·amework. Analysis of the case study showed that tl1e existing generator is 40% larger than necessaty, and the solar system was designed for average month irracliation instead of the lowest montl1, each contributing to sub-optimal system performance.

Four energy supply scenarios were then developed for the case study site: a diesel generator (diesel), two solar PV /diesel (hyb rid) scenarios, and an electricity grid connection. Fuel costs accounted for over two tllirds of operational costs in the hybrid scenarios, and up to 85% for diesel only. Diesel generators were shown to produce over twice the COze emissions of hybrids, and combustion of fuel was shown to conto·ibute 97% of d iesel life-cycle emissions, while sol:or PV module ;ond inverter manufacture contributed 91% of solar system life-cycle emissions. Resulting
C02e payback lor hybrids was 2.5 years and energy payback was 5 years, when compared to diesel.

The levelised cost of electricity LCOE over 25 years for cliesel was between $0.51 and $0.99 /kWh, whereas hybrids were between $0.22 and S0.42 /kWh. Further analysis confirmed that the discounted marginal capital rate for oversizing a solar PV system reduces with surplus capacity, and at 50% Slllplus, the rate was found to be $0.1 0/kWh, less than half the LCOE for hybrid; and 10% to 20% of diesel, and marginally less than the Tanzania electricity tariff.

The success of the NEMe model and the proposed sustainability assessment framework has been demonstrated, and was shown to be beneficial for informing decision-making. Proposed new metrics, Gross Productive Energy (GPe) and Productive Energy Index (Pen were developed and applied to the scenarios and were shown to capture the value of energy, and to quantify the elfectiveness of its utilisation.

Applications of energy utilisation in refugee camps were discussed and included computer access, data connectivity, device charging, a refugee-run radio station and Instant Network Schools (Il\S). These benefits, the relatively low marginal cost of surplus energy in S/kWh, and the annual performance decl ine of solar PV modules, are all convincing arguments for investing in oversized solar PV installations.

At the current level of industry capability and cost, solar PV and hybrid systems provide reduced cost, low impact and self-reliant energy generation for refugee camp water supplies, and the additional capital investment is outweighed by immediate and long term benefits.