Intermittent renewable energy supply combined with electric and thermal energy storage technologies can cover the highest possible share of electricity, heating and cooling needs. However, their integration within the HVAC (Heating, Ventilation and Air-Conditioning) systems could result in far too complex installations, requiring intelligent energy management platforms for achieving their energy-efficient work. This paper introduces a cloud-based control platform, deployed to one such multi-source/sink renewable energy system, that performs all control and monitoring tasks through its hierarchically organized algorithm structure. This cascade control paradigm entails conventional control enrichment by more intelligent superior optimization, which evaluates not only the current energy demand and state of resources but also the inherent flexibility on the demand side and predictive aspects of the local energy production from renewables. On the other hand, the control system layered architecture relies on SCADA system solution, with proven modularity, flexibility and connectivity, making the system easily upgradeable and accessible by the end-users.
The increase in the world's population has led to an enormous increase in the number
of residential and commercial buildings, and thus more frequent installation of air
conditioning, heating and cooling systems, so-called HVAC systems. As they are an
indispensable part of today's living comfort, but also important energy consumers,
their energy efficient work is crucial. Also, it is not uncommon for such systems to be
integrated with non-conventional, renewable, energy sources such as geothermal and
solar energy. It is known that increasing their share leads to a reduction in carbon
dioxide emissions into the atmosphere, helps to improve the security of energy supply
and thus reduces dependence on imports of energy raw materials and electricity.
However, the task of monitoring and controlling energy flow, especially in cases of
systems that integrate multiple different energy sources, storage media and consumer
devices, becomes too complex for human operation, and the question of the
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Commons License Attribution 4.0 International (CC BY 4.0).
portance of using adequate software for these purposes arises. Therefore, this paper
will elaborate on an instance of the advanced, cloud-based, control platform deployed
for one such system, which is, actually, one of the demonstration sites within the
European Horizon 2020 IDEAS project.
The considered multi-source/sink renewable energy system features an HVAC system
with non-standard water-to-water heat pump (HP) integrated hybrid technology that
combines several different renewable energy sources: solar electric and thermal, in
the form of a solar panel (photovoltaic panel) with an additional heat exchanger, in
other words known as a solar collector (photovoltaic thermal collector, PVT),
geothermal horizontal heat exchangers (GHXs) and an air-to-water exchanger (AHX),
Fig. 1. As regards the whole pilot site integrated components, there are, as well,
thermal buffers (BFs) with so-called phase change materials (PCMs) and, finally, radiant
floor and fan coils, as the main air conditioning units. The availability and
costeffectiveness of sources exploitation varies depending on the annual season, time of
day, generally speaking, climatic conditions. For instance, GHX thanks to its large
thermal capacity, is the most stable source, usable both in winter and summer
conditions, for heating or cooling purposes, respectively. Still, its finite capacity prevents
its long-term exploitation, which further leads not only to the disruption of the flora
and fauna of the surrounding land, but also to the reduction of its thermal capacities.
In order to avoid scenario like this, there are various approaches including its
recuperation using remaining sources when the thermal heating demand is not a priority
(UHS mode, Table 1) or, making the alternative energy source sub-optimal choice for
supplying the heat pump system (A, S, AS modes, Table 1). For the purpose of giving
a broader context, the plant could be found in twelve different operating modes [
The control system methodology, algorithmically, consists of two conceptually
separate but collaborative parts of the entire hierarchically organized cascade control
structure: low-level and high-level control [
Namely, deployed supervisory control unit represents an instance of the IMP’s
(Institute Mihajlo Pupin) proprietary VIEW4 SCADA (Supervisory Control and Data
Acquisition) system h/w and s/w technology [
Aside of the expert control system user (precisely called operator), who can directly or remotely access the existing HMI subsystem, there are obvious needs for providing the external end-user interfaces. To provide the interface to the control system, mobile App development requires properly designed API, directly defining the subset of functionalities offered to the external clients and consequently, to the end-users. Briefly, the end-user will be provided with the numerous monitoring capabilities in terms of tracking: active energy flows in the system, production capacity of every single energy source, their share in the heat-pump system supply, state of thermal buffers charge, power consumption of the existing appliances, etc. Previously exposed mostly is focused on the source part of the system, while when it comes to the user side, available will be: relevant weather data, information about indoor space temperature, relative humidity, air-conditioning units (fan coils, radiant floor) impact in achieving thermal comfort and caused temperature/energy distribution in that regard.
Aside of monitoring functionalities, the external interface will be enriched by control actions allowed to be taken by the end-user, such as facility temperature set-point adjustment and decision whether priority goes to the thermal comfort accomplishment and/or DHW (Domestic Hot Water) production or to the cost-effective operating. Taking into account all aforementioned and some preprocessing related to the meaningfulness of the certain mode activation, suitable subset of operating modes can be offered to the end-user for selection. This feature corresponds to the regime known as “Semi-automatic”, realized within the control application running on PLC, with the main difference that for those needs will be implemented with higher level of abstraction, intuitive and self-explanatory for average mobile application user. Optionally, more advanced features like those true operators have could be offered to the privileged users (experienced researchers, from the project consortium, for example) and such a functionality could be supported through the “log-in service” that would return valid tokens, in other words, proper authentication and authorization mechanisms. This and many other possibilities will be thoroughly considered in the extended version of the paper.
The research presented in this paper is partly financed by the European Union (H2020 LAMBDA project, Pr. No: 809965, H2020 IDEAS project, Pr. No: 815271), and partly by the Ministry of Education, Science and Technological Development of Republic of Serbia.