SPEAR (Solar Pyrolysis Energy Access Reactor): Theoretical Design and Evaluation of a Small-Scale Low-Cost Pyrolysis Unit for Implementation in Rural Communities

Cesare Caputo,Ondřej Mašek

doi:10.3390/en14082189

Abstract

Energy access and waste management are two of the most pressing developmental and environmental issues on a global level to help mitigate the accelerating impacts of climate change. They are particularly relevant in Sub–Saharan Africa where electrification rates are significantly below global averages and rural areas are lacking a formal waste management sector. This paper explores the potential of integrating solar energy into a biomass pyrolysis unit as a potentially synergetic solution to both issues. The full design of a slow pyrolysis batch reactor targeted at biochar production, following a strict cost minimization approach, is presented in light of the relevant considerations. SPEAR is powered using a Cassegrain optics parabolic dish system, integrated into the reactor via a manual tracking system and optically optimized with a Monte-Carlo ray tracing methodology. The design approach employed has led to the development an overall cost efficient system, with the potential to achieve optical efficiencies up 72% under a 1.5° tracking error. The outputs of the system are biochar and electricity, to be used for soil amendment and energy access purposes, respectively. There is potential to pyrolyze a number of agricultural waste streams for the region, producing at least 5 kg of biochar per unit per day depending on the feedstock employed. Financial assessment of SPEAR yields a positive Net Present Value (NPV) in nearly all scenarios evaluated and a reasonable competitiveness with small scale solar for electrification objectives. Finally, SPEAR presents important positive social and environmental externalities and should be feasibly implementable in the region in the near term.

Highlights

IntroductionAs part of the growing call to address the accelerators of climate change while balancing the demand for growth in developing countries, energy and waste management are two of the most crucial issues to be addressed [1]
The design and feasibility assessment performed as part of this paper have provided an important step toward the deployment of solar pyrolysis unit for application in rural communities in Sub-Saharan Africa (SSA)
A significant number of uncertainties remain, on how the system will perform in the field, which are essential to address in future work

Summary

Introduction

As part of the growing call to address the accelerators of climate change while balancing the demand for growth in developing countries, energy and waste management are two of the most crucial issues to be addressed [1]. It is estimated that 1.1 billion people still have no access to electricity and 2.8 billion still rely on traditional biomass combustion for cooking or heating demand, largely driven by unsustainable forestry practices or consumption [2]. As a result of vulnerable climate conditions, low development levels and the current lack of appropriate policy frameworks, Sub-Saharan Africa (SSA) is the region expected to be most severely affected by changing climate conditions [4]. While it is estimated that by 2030 the number of people with no access to electricity will decrease to

Methods

Discussion

Conclusion