Laia Ferrer-Martí

A MILP model to design hybrid wind–photovoltaic isolated rural electrification projects in developing countries

Electrification systems based on the use of renewable energy sources are a suitable option for providing electricity to isolated communities autonomously. Wind and hybrid wind–photovoltaic (PV) systems are increasingly getting attention. To electrify scattered communities, designs that combine individual systems and microgrids have recently proven advantageous. In this paper we present a mathematical programming model to optimize the design of hybrid wind–PV systems that solves the location of the wind–PV generators and the design of the microgrids, taking into account the demand of the consumption points and the energy potential. The criterion is the minimization of the initial investment cost required to meet the demand. The proposed hybrid model is tested with realistic size instances and results show the instances are efficiently solved. Moreover, the model is applied to real case studies in Peru; obtained results verify that the hybrid model efficiently finds solutions that significantly reduce costs.

Psychrophilic anaerobic digestion of guinea pig manure in low-cost tubular digesters at high altitude

Guinea pig is one of the most common livestock in rural communities of the Andes. The aim of this research was to study the anaerobic digestion of guinea pig manure in low-cost unheated tubular digesters at high altitude. To this end, the performance of two pilot digesters was monitored during 7 months; and two greenhouse designs were compared. In the dome roof digester the temperature and biogas production were significantly higher than in the shed roof digester. However, the biogas production rate was low (0.04 m(biogas)(3)m(digester)(-3) d(-1)), which is attributed to the low organic loading rate (0.6 kg(VS)m(digester)(-3)d(-1)) and temperature (23°C) of the system, among other factors. In a preliminary fertilization study, the potato yield per hectare was increased by 100% using the effluent as biofertilizer. Improving manure management techniques, increasing the organic loading rate and co digesting other substrates may be considered to enhance the process.

A Community Small-Scale Wind Generation Project in Peru

Electrification systems based on renewable energy have proven to be suitable for providing decentralized electricity to isolated communities. Electricity generated through wind power is one of the technical options available, although infrequently used to date. This article aims to describe the main aspects of technical design, implementation and management of the first small-scale community wind generation project for rural electrification in Peru. This project took place in the community of El Alumbre, in the region of Cajamarca, which is a mountainous area characterized by low to medium wind speeds. This project, implemented by Soluciones Prácticas – Practical Action (Peru), brought electric power to the 33 households (a total of 150 inhabitants) as well as the school and health center of the community.

Optimizing microwind rural electrification projects. A case study in Peru

Electrification systems based on the use of renewable energy sources are suitable for providing electricity to isolated communities autonomously. Specifically, electrification by wind power is one of the technological options that have been used recently in projects implemented in the Andean highlands of Peru. To date, these projects have tended to install individual microwind turbines at each demand point. Alternatively, we propose a solution that considers both individual generators and microgrids. We develop a mathematical model that gives the location and size or type of the wind turbines and the design of the microgrids, taking into account the demand of the consumption points and the wind potential. The criterion is the minimization of the initial investment cost required to meet the demand. The model is validated by application to a real case in the northern highlands of Peru. Results show that microgrids are used despite the village dispersion, and the solutions significantly reduce the initial investment costs.

MILP-based heuristics for the design of rural community electrification projects

Wind-photovoltaic systems are a suitable option to provide electricity to isolated communities autonomously. To design these systems, there are recent mathematical models that solve the location and type of each of the electrification components and the design of the possible distribution microgrids. When the amount of demand points to electrify increases, solving the mathematical model requires a computational time that becomes infeasible in practice. To speed up the solving process, three heuristic methods based on mixed integer linear programming (MILP) are presented in this paper: Relax and Fix heuristics, heuristics based on a Corridor Method and Increasing Radius heuristics. In all algorithms first a relaxed MILP is solved to obtain a base solution and then it is used as a starting point to find a feasible solution by searching in a reduced search space. For each type of heuristic several options to relax and to reduce the solution space are developed and tested. Extensive computational experiments based on real projects are carried out and results show that the best heuristic vary according to the size of instances. The problem of designing electrification projects in rural communities is studied.This problem is hard and heuristics are needed to solve non-small instances.We propose three types of heuristics based on a mathematical model.An extensive computational experiment is carried out to analyse its results.

Experiences of community wind electrification projects in Bolivia: evaluation and improvements for future projects

Currently, early in the XXI century, an estimated 2400 million people depend on traditional biomass for heating and cooking and 1500 million people lack access to electricity (IEA, 2009). Lack of electricity particularly affects rural areas of developing countries (Kanagawa and Nakata, 2008), exacerbating the urban-rural gap. In Bolivia, 35% of the population, more than 3.5 million people do not have access to electricity. Electrification systems based on renewable energy have proved being adequate to provide decentralized electricity to isolated rural communities around the world (Chaureya et al., 2004). These autonomous systems are often much cheaper than the interconnected grid extension and use local resources, avoiding external dependencies which, in turn, promotes long-term sustainability of projects. In particular, micro-wind systems are an alternative with great potential to generate power in rural areas (Lew, 2000), although their use has been limited to date. In South America, a significant institutional effort was made in Argentina to develop rural electrification projects using wind energy in the province of Chubut (Seitz, 2006). In Peru, there are some demonstrative projects of the use of wind power to electrify isolated communities, the first one in El Alumbre (Ferrer-Marti et al., 2010). In Bolivia, the governments policies on rural electrification are governed by the Rural Electrification Regulation, which states that the Department of Energy is responsible for promoting sustainable development, seeking expanded coverage of electricity services throughout the country. Therefore it has the responsibility to update and develop the rural energy strategy, including the Indicative Rural Electrification Plan to facilitate the work of agents in the development of rural electrification. The basic principles that are taken into account are:

Estimating the quality of service of sales in multiplex cinemas using a simulation model

One key decision for managers of multiplex cinemas is how many box offices to open to avoid overstaffing or poor service. We present a simulation model developed to support the capacity management of the Spanish leader of the multiplex cinema sector; the model uses ad hoc collected data. The user introduces the film schedule, the expected audience and the number of opened box offices and the model gives the expected level of service. The company has tested the model and considers that estimates the waiting time correctly and allows adjusting the open box offices to limit the waiting time without overstaffing.