Natale Arcuri

Prototype experimental plant for the interseasonal storage of solar energy for the winter heating of buildings: Description of plant and its functions

The definitive version of an experimental heating plant for buildings which uses thermal energy extracted from an underground water tank heated solely by the sun with interseasonal storage is presented. The entire plant was planned and its functions simulated using calculus codes established at the University of Calabria. The prototype, now in use, consists of a solar radiation collecting field of 91.2 m2, a storage tank of 500 m3, and a building of 1750 m3 which has a thermal requirement of 111 GJ for winter heating. This article describes the constructed prototype of the plant, the procedures carried out that allow the plant to function automatically, and the use, instrumentation, acquisition of experimental data.

First experimental results from a prototype plant for the interseasonal storage of solar energy for the winter heating of buildings

The first experimental results are presented regarding the workings of a plant which uses interseasonal heat stored solely from the sun as an energy source. The results obtained over one year concern radiation collection, the behaviour of the storage system and the satisfaction of the thermal requirements of a building to be heated. The comparison of performance obtained with those predicted by a plant simulation model provided a confirmation of the reliability of the models used for collection and storage tank accumulation. For the latter, the validity of the method used for calculation of heat losses that is the basis for the design of this kind of plant is shown.

Experimental investigation on thermal radiation exchange of horizontal outdoor surfaces

The results of an experimental investigation on thermal radiation exchange between a horizontal surface and the sky are presented. The surface under consideration is the horizontal roof of an air-conditioned room, built for the study of the energy behaviour of buildings. The roof is insulated to create an almost adiabatic boundary condition. The measurement of infrared and solar radiation, together with temperature measurement, was used to determine the net infrared flow, the solar flow absorbed and, by means of the surface thermal balance equation, the convection flow. The experimental investigations allowed the patterns of the surface thermal exchange forming at variation of the boundary conditions to be identified and the problem of evaluating the radiation exchange coefficient and the heat flow rate exchanged in the infrared to be addressed.

Effect of climatic variability on the performance of solar plants with interseasonal storage

A calculation method of the accumulated probability curves from the solar fraction provided by plants with interseasonal solar energy storage is proposed. The variability of the insolation sequences was achieved by randomly generating the monthly clearness indices according to normal distribution, and subsequently, the values of daily available energy by means of Markov’s matrix library [5]. The results obtained from simulations of the generated sequences of collected energy were subjected to experimental verification.

Solar radiation utilisability method in heat pipe panels

In this article the validity of the utilisability method for evacuated heat pipe solar panels was tested, through a comparison of expected useful energy and that measured in an experimental plant. The panels used are distinctive for the working of the heat pipes, which for collection, require a threshold irradiance value higher than the critical, used in quantification of heat losses. Working limits were identified and the basal utilisability calculation hypotheses tested by using a calculation code that simulates heat pipe behaviour. Dynamic phenomena linked to inertia during collection were studied with a mathematical model constructed from results provided by the collectors field at stepped variation to solar irradiance. The numerical and experimental results enable a critical comparison between calculated and measured energy.

Real Costs Assessment of Solar-Hydrogen and Some Fossil Fuels by means of a Combustion Analysis

In order to compare solar-hydrogen and the most used fossil fuels, the evaluation of the “external” costs related to their use is required. These costs involve the environmental damage produced by the combustion reactions, the health problems caused by air pollution, the damage to land from fuel mining, and the environmental degradation linked to the global warming, the acid rains, and the water pollution. For each fuel, the global cost is determined as sum of the market price and of the correspondent external costs. In order to obtain a quantitative comparison, the quality of the different combustion reactions and the efficiency of the technologies employed in the specific application sector have to be considered adequately. At this purpose, an entropic index that considers the degree of irreversibility produced during the combustion process and the degradation of surroundings is introduced. Additionally, an environmental index that measures the pollutants released during the combustions is proposed. The combination of these indexes and the efficiency of the several technologies employed in four energy sectors have allowed the evaluation of the total costs, highlighting an economic scenario from which the real advantages concerning the exploitation of different energy carrier are determined.

A Smart Air-Conditioning Plant for Efficient Energy Buildings

The spread of renewable energy technologies in the building sector has produced the new figure of “prosumer”, able to consume and produce energy simultaneously. In this context, a correct management of the energy fluxes is required to increase user remuneration. All of this, paired with the use of the emergent IoT technologies, allowed the realization of a Smart Ecosystem devoted to make effective the process of producing, storing and consuming energy. Considering PV generators, the self-produced electricity surplus has to be transferred with advantageous conditions, alternatively it has to be stored. Air-conditioning plants employing heat pumps represent a useful option for the rational management of renewable electricity because the same system can be used as an alternative to “electric storage”, cheaper and more reliable than traditional batteries. Heat pumps can be exploited to produce thermal or cooling energy and store it in a suitable tank, though the building does not require them, and to conciliate the time shift between energy demand and offer. In presence of a saturated storage tank, the same building could be used as a further thermal accumulator by exploiting radiant emission systems to activate its thermal mass, by means of either overheating or undercooling strategies. The combination of these solutions allows for noticeable energy and economic savings and a rational use of renewable sources. However, a smart control system is required to make all the various involved devices communicating and coordinating among each other. A smart air conditioning system and the correspondent control strategies adopted for its management, based on the employment of PV driven heat pumps with thermal storage connected to a radiant emission system, is introduced.

Characterization of Glauber Hydrate Salt, Recoverable from the Disposal of Lead Batteries, When Used for Thermal Energy Storage

Disposal process of lead batteries allows recovering not only lead but also sodium sulphate that could be used for the production of a very interesting material.

Energy Recovery from the LNG Regasification Process

The global request of natural gas (NG) is continuously increasing, consequently also the regasification of liquefied natural gas (LNG) is becoming a process largely employed. Liquefied natural gas at a temperature of around 113 K at atmospheric pressure has to be regasified for its transportation by pipeline. The regasification process makes the LNG exergy available for various applications, particularly for the production of electrical energy. Different possibilities to exploit the thermal energy released during regasification are available. New plant configurations whose functioning does not constrain the processes of the regasification terminal are proposed. A possible solution is LNG exploitation as a cold source for ocean thermal energy conversion (OTEC) power plants. Electric energy can be produced also by the exploitation of heat released from hot sources, for instance, the condensation heat of power plants by means of consecutive thermodynamic cycles. The rational use of the cold source (LNG) allows the increment of electrical production and growth of the thermodynamic efficiency, with corresponding environmental benefits.

Data demonstrating the influence of the latent storage efficiency on the dynamic thermal characteristics of a PCM layer

Dynamic thermal characteristics, for each month of the year, of PCM layers with different melting temperatures and thermophysical properties, in a steady periodic regime, were determined (Mazzeo et al., 2017 [1]). The layer is subjected to climatic conditions characterizing two locations, one with a continental climate and the second one with a Mediterranean climate. This data article provides detailed numerical data, as a function of the latent storage efficiency, including monthly average daily values: of the latent energy fraction, of the decrement factors of the temperature, of the heat flux and of the energy, and of the time lags of the maximum and minimum peaks of the temperature and of the heat flux.