• Energy Research

Fouling mitigation is paramount to maintaining the reliable and efficient operation of a heat exchanger network (HEN). From the operational perspective, fouling can be mitigated by changing the flo...

Integrated biomass solar town concept is a concept which encourages local community to utilize biomass waste comprehensively with strong ties between community and local stakeholders. This paper discusses about an Integrated Biomass Solar Town for eco village with and without load shifting (LS). On the other hand, the energy storage (ES) is also incorporated which could help cut electricity demand during peak periods and smoothing variations in power generation by variable solar power. A substantial technical and economic benefit was achieved through the implementation of integrated (LS) and ES. In this study, LS is used mainly to increase demand during periods of high supply and also shift the load to interval with low demand hence reduce the size of ES significantly. The concept is one of the great initiatives to spur economic growth and environmental protection through energy efficiency improvement and deployment of low-carbon technologies.

Abstract Fouling is a major source of energy inefficiencies that decreases the performance of process units. Fouling mitigation alternatives are required to ensure a sustainable, profitable, and safe operation. In heat exchanger networks, two mitigation alternatives are: flow distribution control, and periodical cleanings. This paper addresses the optimal control and optimal cleaning scheduling, individually and simultaneously, for heat exchangers in refining operations. The problem is formulated as a MINLP, which uses an accurate model of the process, logic disjunctions, and a continuous time representation. To solve it efficiently, it is reformulated as a mathematical program with complementarity constraints (MPCC). The modelling and solution strategies are demonstrated in several case studies, from small to moderately large networks for realistic applications. The formulation is versatile, and large network problems are solved in a reasonable computational time. The integration of optimal scheduling and control decreases the operational cost substantially relative to independent mitigation alternatives.

This work proposes a novel approach called stand-alone hybrid system power pinch analysis (SAHPPA), which is particularly applicable for the design of off-grid distributed energy generation systems. The enhanced graphical tool employs new ways of utilising the recently introduced demand composite curve and supply composite curve while honouring and adapting fundamental energy systems engineering concepts. The SAHPPA method is capable of optimising the capacity of both the power generators and energy storage for biomass (i.e. non-intermittent) and solar photovoltaic (i.e. intermittent) energy technologies, which is a contribution to the emerging area of power pinch analysis. In addition, the procedure considers all possible efficiency losses in the overall system encompassing the charging–discharging and current inversion processes.

Abstract Concentrated Solar Power (CSP) plants capture abundantly available solar radiation and offer a renewable energy supply. The optimal design and operation of air coolers in such plants is key to their efficiency, however their dynamic performance is impaired due to fouling and variable external conditions. First, the air cooler section design is optimally designed in a modular way, enabling their use as a network of exchangers that can be operated independently. Then, exploiting the extra degrees of freedom, their simultaneous optimal operation and cleaning scheduling over 10 years is considered using a suitable formulation, with an economic objective function. Seasonal variability and operating conditions uncertainty are included. The resulting mixed-integer non-linear programming (MINLP) problem is solved efficiently using a Benders decomposition approach. Results are presented for two realistic CSP plants in Almeria (Spain) and Dubai (United Arab Emirates), which have different external and weather conditions. The optimal solution reduces operating cost and defines optimal cleaning policies which are location dependent.

The performance and operability of heat exchanger networks (HENs) is strongly affected by fouling, which involves the deposition of unwanted material, which reduces the heat-transfer rate and incre...

We assess the technoeconomic feasibility of onsite electricity and steam generation from recovered low-grade thermal energy in oil refineries using organic Rankine cycle (ORC) engines and mechanical vapour compression (MVC) heat pumps in various countries. The efficiencies of 34 ORC and 20 MVC current commercial systems are regressed against modified theoretical models. The resulting theoretical relations predict the thermal efficiency of commercial ORC engines within 4–5% and the coefficient of performance (COP) of commercial MVC heat pumps within 10–15%, on average. Using these models, the economic viability of ORC engines and MVC heat pumps is then assessed for 19 refinery streams as a function of heat source and sink temperatures, and the available stream thermal energy, for gas and electricity prices in selected countries. Results show that: (i) conversion to electrical power with ORC engines is, in general, economically feasible for heat-source temperatures >70 °C, however with high sensitivity to energy prices; and (ii) steam generation in MVC heat pumps, even more sensitive to energy prices, is in some cases not economical under any conditions—it is only viable with high gas/low electricity prices, for large heat sources (>2 MW) and higher temperatures (>140 °C). In countries and conditions with positive economics, payback periods down to two years are found for both technologies.

Modelling of crude oil fouling in heat exchangers has been traditionally limited to a description of the deposit as a thermal resistance. However, consideration of the local change in thickness and the evolution of the properties of the deposit due to ageing or changes in foulant composition is important to capture the thermal and hydraulic impact of fouling. A dynamic, distributed, first‐principles model of the deposit is presented that considers it as a multicomponent varying‐thickness solid undergoing multiple reactions. For the first time, full cleaning, partial cleaning, and fouling resumption after cleaning can be simulated in any order with a single deposit model. The new model, implemented within a single tube framework, is demonstrated in a case study where various cleaning actions are applied following a period of organic deposition. It is shown that complete mechanical cleaning and chemical cleaning of different extent, according to a condition‐based efficacy, can be seamlessly simulated. © 2015 American Institute of Chemical Engineers AIChE J, 62: 90–107, 2016