Article
The Comparison of Different Types of Heat
Accumulators and Benefits of Their Use
in Horticulture
Sławomir Kurpaska
1
, Jarosław Knaga
1
, Hubert Latała
1
, Michał Cupiał
1,
* ,
Paweł Konopacki
2
and Ryszard Hołownicki
2
1
Faculty of Production Engineering and Energetics, University of Agriculture in Krakow, ul. Balicka 116B,
30-149 Kraków, Poland; rtkurpas@cyf-kr.edu.pl (S.K.); jaroslaw.knaga@ur.krakow.pl (J.K.);
hubert.latala@urk.edu.pl (H.L.)
2
Research Institute of Horticulture, ul. Konstytucji 3 Maja 1/3, 96-100 Skierniewice, Poland;
Pawel.Konopacki@inhort.pl (P.K.); ryszard.holownicki@inhort.pl (R.H.)
* Correspondence: michal.cupial@ur.krakow.pl; Tel.: +48-12-662-46-23
Received: 22 January 2020; Accepted: 3 March 2020; Published: 5 March 2020
Abstract:
This paper presents the results of the analysis of thermal issues and energy efficiency of
three types of accumulators; namely stone-bed; water and phase change. Research experiments
were carried out during April–October 2013 in a standard commercial semi-cylindrical high plastic
tunnel with tomato cultivation of 150 m
2
. A stone-bed accumulator; with an area of almost 75 m
2
was installed in the tunnel below ground level; while a water accumulator with a volume of 4 m
3
was installed outside the tunnel. A phase change material (PCM) accumulator, with a volume of
1 m
3
containing paraffin, was located inside the tunnel. The heat storage capacity of the tested
accumulators and the energy efficiency of the process were determined based on the analyses of
the 392 stone-bed charging and discharging cycles, the 62 water accumulator charging cycles and
close to 40 PCM accumulator charging and discharging cycles. Dependencies in the form of easily
measurable parameters; have been established to determine the amount of stored heat; as well as the
conditions for which the effectiveness of these processes reaches the highest value. The presented
analysis falls under the pro-ecological scope of replacing fossil fuels with renewable energy. As a
result of the analysis; it was found that; in the case of a stone-bed; such an accumulator shows higher
efficiency at lower parameters; that is, temperature difference and solar radiation intensity. In turn;
a higher temperature difference and a higher value of solar radiation intensity are required for the
water accumulator. The energy storage efficiency of the PCM accumulator is emphatically smaller
and not comparable with either the stone-bed or the water accumulator.
Keywords: accumulators; plastic tunnel; energy; efficiency; sensor
1. Introduction
Currently, the overwhelming majority of the world’s energy comes from non-renewable sources,
such as oil, coal, natural gas and uranium, which causes greenhouse gas emissions, global warming and
related climate change. Counteracting these adverse phenomena is a huge challenge for modern science
and the economy, resulting in the need to conduct research into the possibility of using renewable
energy sources as alternatives [
1
–
3
], with solar energy and methods of its acquisition, processing and
storage being the most promising [
4
]. The high potential for the use of heat obtained from solar energy
results from the high efficiency of storage and conversion of this energy [
5
]. The basic elements used in
this field are solar collectors and heat storage systems. Scientific research, conducted for many years,
has been aimed at developing appropriate accumulators that will allow energy storage and will be
Sensors 2020, 20, 1417; doi:10.3390/s20051417 www.mdpi.com/journal/sensors
