Sequential management of optimally-designed thermal storage tanks for multi-energy district boilers

Abstract

International audienceAs part of the second phase of the OptiEnR research project, the present work focuses on optimizing multi-energy district boilers by adding thermal storage tanks to the plants. First, both a parametric study and a simulation-based evaluation of the thermal losses are carried out in order to design the hot water tanks. Next, a sequential management approach, based on the power demand and the characteristics of the biomass unit(s), is defined with the aim of improving efficiency. Energy and economic criteria are proposed and evaluated in order to highlight the configurations that meet needs and expectations. The way thermal energy storage impacts on the boiler units dynamics is evaluated in simulation. Finally, the proposed approach has been applied to two multi-energy district boilers equipped with one and two biomass units, respectively. The plants are managed by Cofely GDF-Suez, our industrial partner in the project. The results highlight the ability of a hot water tank (when it is optimally designed and managed) to improve the operation of a multi-energy district boiler and realize significant economic savings. As a key point, the excess of energy produced by the biomass unit(s) during low-demand periods can be stored and released when demand is high, instead of engaging a gas boiler

Techno-Economic Analysis of Latent Heat Thermal Energy Storage Integrated Heat Pump for Indoor Heating

“…kg/m 3 864*/760 *calculated from the volume expansion Height-to-diameter ratio (H/D) is a crucial parameter in designing a thermal energy storage tank. The increase of H/D can improve the charging and discharging efficiency and reduce the occupied area, while it also results in increased weight and cost of the tank, and in increased heat loss [45][46][47]. Considering the charging/discharging time and required heat capacity, the H/D was set as 1.7 with inner diameter of 0.6 m. A 2D axis-symmetrical model was built to simulate the thermal processes of LHTES, shown in Figure 6.…”

Predictive Control of Thermal Storage Systems Designed for Multi-Energy District Boilers: a Case Study in France

“…4 depicts the MPC algorithm used. At each time step , a simulation over the forecast horizon based on the non-predictive (sequential) strategy (Labidi et al, 2014), the current amount of energy stored in the tank, and the forecasted values of is performed in order for the values of [ ( / ), … , ( + − 1/ )] to be initialized. These values are then optimized using both the non-linear optimization algorithm "fmincon'' from Matlab ® and the developed model of the multi-energy district-boiler.…”

“…First, we assessed a specific case study (Eynard et al, 2012) and we are now developing a flexible and generalized approach. It has been highlighted in a previous work that once optimally designed and managed using a sequential approach based on logical conditions, a thermal storage tank can significantly improve the overall efficiency of a plant, in particular in case of badly-sized heat generators (Labidi et al, 2014). So, the present paper deals with the optimal management of a thermal storage tank using a Model Predictive Controller (MPC).…”