In summer 2021, Greece was impacted by what is considered to be ‘its worst heatwave in more than 30 years’ [12]. With close to record-breaking temperatures of 46-degrees Celsius [13], wildfires have caused residents near Athens to flee their homes. This heatwave is considered to be the worst since July 1987, when over one thousand deaths were recorded in and around the capital in the period 20–31 July [14]. One concomitant cause of these fatalities was the heat stress experienced by residents when daytime air temperatures ranged between 40–45 degrees Celsius [14]. It should be noted that cooling technologies were then not as widely accessible as they are today. Given that a major proportion of the energy demand of the Greek hotel sector is attributable to cooling [8], the use of air conditioning can be expected to have risen even further throughout the 2021 heatwave, and in general, given the increasing frequency of such heatwaves caused by climate change. This means that in order to meet the increased cooling demand, Rhodian fossil fuel power plants will be operating at maximum capacity, thereby further exacerbating climate change. Moreover, the unreliability of NII energy systems causes frequent blackouts and energy shortages during periods of high demand [10]. Loss of electricity for cooling is a major risk during heatwaves when heat stress has proven to be a threat to human health [14]. The rise in heatwave frequency and extremity, coupled with the increased risk of energy shortages, demonstrates the importance of creating self-sustaining energy systems with an increased share of RES in energy production.

In the wake of the current climate crisis, Greece plans to connect most of its NIIs with the mainland by 2030 [15]. This will have a positive impact on the energy system of Rhodes, not only generating a more efficient and reliable energy supply but also reducing the currently high energy production costs associated with the import of fossil fuels [10]. The Greek National Energy and Climate Plan has set out specific objectives to attain energy and climate goals by 2030 [15]. These objectives include a reduction in greenhouse gas emissions by over 56% compared with 2005 emission levels, an increase in the share of RES in energy consumption to a minimum of 35%, and greater efficiency of energy use [15]. To support this initiative, a number of schemes have been implemented to help private individuals, small businesses, and public entities to expand the proportion of RES in their energy mix. An initiative of specific interest in this context is a support scheme for electricity generation by means of PV panels on both the mainland and NIIs [16]. This scheme is a net metering programme that allows users who produce their own electricity by means of PV systems to export their surplus energy back to the grid. It has to be noted that in the framework of net metering, maximum capacity limits are defined for the installed PV systems: for non-interconnected islands, PV systems need to be smaller than 10 kWp or have less than 50% of the agreed power consumption [16]. For the hotel under investigation, 50% of the agreed electricity consumption of 265.8 kW is not reached even with maximum expansion, so the expansion of PV in the case presented here is not limited by the maximum capacity limit. Incentives of this kind encourage individuals to increase the share of RES in energy production and thus contribute to reducing carbon emissions.

A wide range of studies have already analysed the most effective methods of reducing carbon emissions in energy production. For the purposes of this report, papers analysing sustainable island energy systems and individual residential energy systems were evaluated in order to identify appropriate strategies to reduce carbon emissions within the tourist accommodation sector on NIIs.

The high costs associated with fuel imports, the vast RES potential available on Greek islands, and the National Energy and Climate Plan initiatives have provided an incentive for various Greek NIIs to maximise the use of RES in their energy systems in recent years. A string of Greek islands are currently striving towards or have already achieved a self-sustained or carbon-neutral energy supply (Table 1). However, inadequate interconnection to the mainland poses a number of challenges to the integration of high RES ratios [17]. Given the intermittent nature of RES, guaranteeing sufficiently high energy storage capacity to accommodate excess power generation during high generation periods (e.g., high solar irradiance or optimal wind conditions) is particularly critical in this context [11].

Analysis of studies on the carbon reduction in European hotels or buildings highlights that the following factors contribute to promoting sustainability in the accommodation sector as a whole:

• Improving a building’s structure to enhance energy efficiency and prevent unnecessary heat losses/gains [8,22];
• Incorporating renewable energy technologies [10,18,20];
• Implementing energy-saving strategies—inter alia key cards, thermostat controls and energy-saving light bulbs [8]—to reduce energy consumption;
• Understanding public perception as a critical element in promoting the popularity of ‘green hotels’ [23];
• Hotels are ultimately businesses that seek financial gain [8], hence the importance of optimising a hotel energy system in terms of both carbon emissions and costs.