• Energy Research

Publicly available toolkits for cost calculation in renewable energy projects were reviewed, and their main characteristics, strengths and weaknesses identified. An original Life-Cycle Cost (LCC) modelling toolkit was developed to address some of the identified shortcomings, and to facilitate the calculation of costs of electrical and thermal energy from biomass-based processing pathways. The toolkit was used to compare the Levelized Cost of Energy (LCOE) for electricity and/or heat generation for a ‘Bioenergy Case’, after the adoption of bioenergy technology, and compared with equivalent costs under a business-as-usual ‘Base Case’, for selected commercial demand sectors in Sub-Saharan Africa, within a 10 kW to 5 MW scale range. Case Studies of the toolkit’s application are described for a smallholder tea factory in Kenya, a wood processing enterprise in Tanzania and an oil palm mill in Ghana, which illustrate its ability to model energy production based on both combustion and anaerobic digestion, under various heat, power and combined heat and power configurations. Sensitivity analysis was carried out to determine the effect on LCOEheatand LCOEelectricityof adjustments in key operating parameters, such as biomass feedstock cost, feed-in tariff for export of surplus power to the grid or on-site energy demand. The versatility of the LCC toolkit enables bioenergy projects to be modelled from different perspectives (biomass feedstock diversification, conversion pathways or business models) and for different users (plant managers, project developers or potential investors), and it can be customised and adapted as prices, legislation and technical aspects evolve with time.

Hybrid renewable energy systems (HRES) have been widely identified as an efficient mechanism to generate electrical power based on renewable energy sources (RES). This kind of energy generation systems are based on the combination of one or more RES allowing to complement the weaknesses of one with strengths of another and, therefore, reducing installation costs with an optimized installation. To do so, optimization methodologies are a trendy mechanism because they allow attaining optimal solutions given a certain set of input parameters and variables. This work is focused on the optimal sizing of hybrid grid-connected photovoltaic-wind power systems from real hourly wind and solar irradiation data and electricity demand from a certain location. The proposed methodology is capable of finding the sizing that leads to a minimum life cycle cost of the system while matching the electricity supply with the local demand. In the present article, the methodology is tested by means of a case study in which the actual hourly electricity retail and market prices have been implemented to obtain realistic estimations of life cycle costs and benefits. A sensitivity analysis that allows detecting to which variables the system is more sensitive has also been performed. Results presented show that the model responds well to changes in the input parameters and variables while providing trustworthy sizing solutions. According to these results, a grid-connected HRES consisting of photovoltaic (PV) and wind power technologies would be economically profitable in the studied rural township in the Mediterranean climate region of central Catalonia (Spain), being the system paid off after 18 years of operation out of 25 years of system lifetime. Although the annual costs of the system are notably lower compared with the cost of electricity purchase, which is the current alternative, a significant upfront investment of over $10 M - roughly two thirds of total system lifetime cost - would be required to install such system. (C) 2015 Elsevier Ltd. All rights reserved.

This paper proposes a hybrid renewable energy system (HRES) consisting of photovoltaic (PV), wind and forest wood biomass power for cogeneration, and applies a multi-objective optimization methodology to study the trade-offs between life-cycle cost and environmental impact (EI) of such a system. The optimization is achieved by applying an operation strategy that maximizes the efficiency of the biomass power subsystem coupled with an optimization model based on the use of genetic algorithm (GA) to obtain the optimal system sizing. The system is designed to supply the electricity demand of a rural township and the thermal demand – both heating and sanitary hot water (SHW) – of a neighborhood in a district heating (DH) scheme. Indigenously available renewable energy sources (RES) are used, taking special care in the case of biomass to not exceed the self-growth rate of local tree species. Results show that by taking advantage of the thermal energy produced, the payback time of the investment required to install the system is significantly reduced, being profitable after 9 years. Furthermore, it is also observed that layouts with low costs have greater EI and vice versa. However, it is shown that moderate cost increases have great returns on EI reduction.

In the current energy conjunction, with an expected growth of energy consumption in a context of fossil fuel depletion, more focus is being placed on renewable energy sources (RES) for electricity generation. One of the most appealing alternatives is biomass, which can be efficiently used to generate electricity as well as heat with the application of cogeneration technologies that enhance the efficiency of the entire energy conversion process. The Mediterranean basin is a region with a recognized potential for electricity and heat production using primary forest biomass and sub-products from sawmills, among which highlight wood chips for their easiness to be obtained, processed and dried as well as for their good and stable burning or gasification behavior. However, in order to efficiently use the available resources, that is, minimizing logistical requirements to reduce the energy necessary for the electricity generation process, the biomass found in Mediterranean forests can only be used at micro- and small-scale levels to be compatible with sustainable forestry practices. This article is aimed to describe the different technological alternatives to convert wood chips into electricity and heat and it also reviews and compares the current performances in terms of efficiency of these technologies at the micro- and small-scale levels. Peer Reviewed

Hybrid renewable energy systems (HRES) are a trendy alternative to enhance the renewable energy deployment worldwide. They effectively take advantage of scalability and flexibility of these energy sources, since combining two or more allows counteracting the weaknesses of a stochastic renewable energy source with the strengths of another or with the predictability of a non-renewable energy source. This work presents an optimization methodology for minimum life cycle cost of a HRES based on solar photovoltaic, wind and biomass power. Biomass power seeks to take advantage of locally available forest wood biomass in the form of wood chips to provide energy in periods when the PV and wind power generated are not enough to match the existing demand. The results show that a HRES combining the selected three sources of renewable energy could be installed in a rural township of about 1300 dwellings with an up-front investment of US $7.4 million, with a total life cycle cost of slightly more than US $30 million. Such a system would have benefits in terms of energy autonomy and environment quality improvement, as well as in term of job opportunity creation.

This work describes a methodology to optimize a grid-connected hybrid renewable energy system (HRES) that hybridizes photovoltaic, wind and forest biomass energy sources taking into account cost and environmental impact criteria from a life-cycle perspective. The developed model has been tested in a sample township in central Catalonia. The results show that life-cycle cost and life-cycle environmental impact are contradicting criteria. Low environmental impact layouts highly dependent on RES have higher costs than the ones more reliant on the electricity from the public grid, which present high environmental impact. A sensitivity analysis has been performed to analyze the trade-offs between different energy sources of the system, showing that wind power is the RE source with higher impact on the system since it presents lower cost and lower environmental impact, compared with biomass and photovoltaic power. Another important conclusion that can be drawn from such sensitivity analysis is that improving the rate of return on investment in HRES would be a very beneficial measure to encourage the use of renewable energies for electricity production, as it has significant positive outcomes in terms of both cost and environmental impact reduction. Peer Reviewed