**1. Introduction: Health and Energy**

The energy systems most modern economies rely on are outmoded and unhealthy, which has multiple significant negative impacts. In addition to anthropogenic climate change caused by greenhouse gas emissions, nitrogen and sulfur oxides and carbon particulates damage ecosystems and are harmful to human health. Excess mortality from outdoor air pollution due to fossil fuel use is estimated at four million people per year [1]. The economic costs of this air pollution were estimated at USD 2.9 trillion, or over three percent of global GDP in 2018 [2].

Discussion of the relationship between climate change and health is increasing, most recently as the COVID-19 pandemic has highlighted improvements in air quality from reductions in human activity. Addressing this issue more permanently is a challenge; however, it is not a wicked problem as solutions can be mutually beneficial. Tackling the climate emergency goes hand-in-hand with improving public health outcomes by reducing harmful air pollution and developing a circular economy based on renewable energy ecosystems. Hakovirta and Denuwara now suggest 'sustainability' be redefined as "the intersection of the economy, environment, society and human health" [3]. The link to health represents an opportunity to accelerate the transition to renewable energy, not least because the health system itself is in a unique position to lead.

Doctors have had considerable success framing this health-related sustainability challenge, raising awareness of the considerable price that humanity pays for an energy ecosystem that relies on fossil fuels [4]. The Sustainable Development Unit of the UK National Health Service (NHS) was established in 2008, and the NHS has since reduced its carbon footprint by 19 percent over the 10 year period to 2018 [5]. Analysis of these efforts was published in *The British Medical Journal* [6]. Other prestigious medical journals have been amplifying calls to action, with editorials published in *The Lancet* [7], *The New England Journal of Medicine* [8] and *The Medical Journal of Australia* [9].

These efforts are critical because the health sector has a significant environmental footprint. In Australia, health care represented seven percent of Australia's carbon dioxide (CO2) emissions in 2014–2015, with over one third of that attributable to public hospitals [10]. Leadership here can have a more pervasive impact since public perception of technology and its safety is important for its acceptance and deployment [11,12]. Doctors and scientists are the two most trusted professions [13], and so have a vital role to play in driving the innovative and creative thinking that will move past just efficiency and recycling to deliver whole system sustainable health services [14].

Systems thinking research supports the concepts of industrial ecology and social ecology that acknowledge connections between organizations and society and the importance of this for driving long-term change [15]. Collective visions of promising techno-scientific futures can legitimize investments and transcend uncertainty [16]. Public energy installations and community energy services are already being used for community interaction with new energy technologies [17,18]. Communities have shown a willingness to invest directly in renewable energy installations and there is interest and receptivity of these installations specifically in the hospital context [19].

Hospitals, as critical and major piece of publicly funded infrastructure, are an excellent case study for energy ecosystems. A hospital is not simply an energy user, it is a community and industry hub. Hospitals are regarded as safe havens, resilient facilities for disaster and emergencies [20]. Large numbers of staff and public use them daily and on-site parking is necessary for patients, staff and for ambulances, as well as commercial delivery vehicles. The hospital facility itself requires extremely secure sources of heat and power, oxygen and water.

Using data from the NHS, heat and power accounted for only 17 percent of the carbon footprint of UK hospitals in 2017 [21]. Supply chain and services accounted for 54 percent, while travel and transport, including staff commuting, accounted for 16 percent. Manufactured fuels, chemicals and gases represented another four percent. This presents an opportunity to consider this power and resource demand holistically.

In Australia, backup power supply for hospitals has been identified as a government priority for projects to drive innovation and demonstrate capability [22]. Renewable technologies can do more than provide backup power, however—they can play a critical role in reimagining a sustainable energy ecosystem. Integrating production and storage solutions in distributed systems presents an opportunity to optimize hybrid systems including the use of hydrogen and batteries [23].

The following multi-generation design concept shows how we envision that sustainable energy technologies can transform a hospital from a resource sink to the centerpiece of a new reliable and healthy energy ecosystem. We assess relevant technologies and integrate them for a hypothetical hospital in New South Wales (NSW), Australia. This located approach provides some grounding for

the design and discussion, though we note the same approach is widely applicable and we aim to inspire similar developments elsewhere. *Sustainability* **2020**, *12*, x FOR PEER REVIEW 3 of 17

### **2. Materials and Methods: Technology Assessment and Design Approach** *Sustainability* **2020**, *12*, x FOR PEER REVIEW 3 of 17 **2. Materials and Methods: Technology Assessment and Design Approach**

There are a range of technologies available to fulfill the multitude of resource requirements of a hospital. Presented here is a selection of technologies available to supply reliable power and the other associated needs for this healthcare system. We frame the design research to revolve around three key atoms: hydrogen, oxygen and carbon. The strengths, weaknesses and potential co-benefits of the individual technologies are discussed and summarized. This assessment is then used to develop sustainable hospital power system concepts through multidisciplinary design that simultaneously responds to carbon emissions, health impacts and material sustainability. **2. Materials and Methods: Technology Assessment and Design Approach**  There are a range of technologies available to fulfill the multitude of resource requirements of a hospital. Presented here is a selection of technologies available to supply reliable power and the other associated needs for this healthcare system. We frame the design research to revolve around three key atoms: hydrogen, oxygen and carbon. The strengths, weaknesses and potential co-benefits of the individual technologies are discussed and summarized. This assessment is then used to develop sustainable hospital power system concepts through multidisciplinary design that simultaneously responds to carbon emissions, health impacts and material sustainability. There are a range of technologies available to fulfill the multitude of resource requirements of a hospital. Presented here is a selection of technologies available to supply reliable power and the other associated needs for this healthcare system. We frame the design research to revolve around three key atoms: hydrogen, oxygen and carbon. The strengths, weaknesses and potential co-benefits of the individual technologies are discussed and summarized. This assessment is then used to develop sustainable hospital power system concepts through multidisciplinary design that simultaneously responds to carbon emissions, health impacts and material sustainability.

### *2.1. Power Generation 2.1. Power Generation 2.1. Power Generation*

### 2.1.1. Diesel Combustion 2.1.1. Diesel Combustion 2.1.1. Diesel Combustion

Coal has been the mainstay for the supply of power since the first Industrial Revolution, powering centralized electricity grids. Oil helped power the second Industrial Revolution, and a typical hospital relies on diesel internal combustion engine (ICE) generators for emergency power as shown in Figure 1. These stand-by engines are not designed to run for extended periods and so remain idle for most of their life. When the added burden of maintenance is considered, this is an expensive means of meeting mandated requirements. Coal has been the mainstay for the supply of power since the first Industrial Revolution, powering centralized electricity grids. Oil helped power the second Industrial Revolution, and a typical hospital relies on diesel internal combustion engine (ICE) generators for emergency power as shown in Figure 1. These stand-by engines are not designed to run for extended periods and so remain idle for most of their life. When the added burden of maintenance is considered, this is an expensive means of meeting mandated requirements. Coal has been the mainstay for the supply of power since the first Industrial Revolution, powering centralized electricity grids. Oil helped power the second Industrial Revolution, and a typical hospital relies on diesel internal combustion engine (ICE) generators for emergency power as shown in Figure 1. These stand-by engines are not designed to run for extended periods and so remain idle for most of their life. When the added burden of maintenance is considered, this is an expensive means of meeting mandated requirements.

**Figure 1.** Conventional system with diesel backup during normal operation. **Figure 1.** Conventional system with diesel backup during normal operation. **Figure 1.** Conventional system with diesel backup during normal operation.

### 2.1.2. Gas Combustion 2.1.2. Gas Combustion

air pollution.

2.1.2. Gas Combustion Co-generation or tri-generation captures thermal energy from combustion that would otherwise be wasted and deploys it for heating and cooling using absorption chillers. As hospitals have balanced power requirements and their heat requirements do not typically exceed the temperature for steam sterilization (below 160 °C), they make ideal candidates for using combined heat and power systems (CHP) [24]. This opportunity was identified more than a decade ago [25] and many hospitals have used this opportunity to improve energy efficiency, reduce costs and reduce emissions [26]. Hospital CHP installations use engines or gas turbines burning natural gas from existing networks as shown in Figure 2. This is an improvement on coal-fired power, though these systems still produce Co-generation or tri-generation captures thermal energy from combustion that would otherwise be wasted and deploys it for heating and cooling using absorption chillers. As hospitals have balanced power requirements and their heat requirements do not typically exceed the temperature for steam sterilization (below 160 ◦C), they make ideal candidates for using combined heat and power systems (CHP) [24]. This opportunity was identified more than a decade ago [25] and many hospitals have used this opportunity to improve energy efficiency, reduce costs and reduce emissions [26]. Hospital CHP installations use engines or gas turbines burning natural gas from existing networks as shown in Figure 2. This is an improvement on coal-fired power, though these systems still produce air pollution. Co-generation or tri-generation captures thermal energy from combustion that would otherwise be wasted and deploys it for heating and cooling using absorption chillers. As hospitals have balanced power requirements and their heat requirements do not typically exceed the temperature for steam sterilization (below 160 °C), they make ideal candidates for using combined heat and power systems (CHP) [24]. This opportunity was identified more than a decade ago [25] and many hospitals have used this opportunity to improve energy efficiency, reduce costs and reduce emissions [26]. Hospital CHP installations use engines or gas turbines burning natural gas from existing networks as shown in Figure 2. This is an improvement on coal-fired power, though these systems still produce air pollution.

**Figure 2.** Combined heat and power system connected to both gas and electricity networks. **Figure 2. Figure 2.**  Combined heat and power system connected to both gas and electricity networks. Combined heat and power system connected to both gas and electricity networks.

### 2.1.3. Fuel Cells 2.1.3. Fuel Cells

Commercial solid oxide fuel cell (SOFC) units in operation today generally include integrated steam methane reforming (SMR) equipment to use natural gas as a fuel source, which is broken apart to extract hydrogen. The high operating temperature and water 'exhaust' from the hydrogen fuel cell make this combination efficient and well suited for CHP systems. An advantage of this approach compared to simply burning the natural gas in an engine or turbine is the near complete elimination of harmful air pollutants (NOx, SO<sup>x</sup> and particulates). Commercial solid oxide fuel cell (SOFC) units in operation today generally include integrated steam methane reforming (SMR) equipment to use natural gas as a fuel source, which is broken apart to extract hydrogen. The high operating temperature and water 'exhaust' from the hydrogen fuel cell make this combination efficient and well suited for CHP systems. An advantage of this approach compared to simply burning the natural gas in an engine or turbine is the near complete elimination of harmful air pollutants (NOx, SOx and particulates).

*Sustainability* **2020**, *12*, x FOR PEER REVIEW 4 of 17

Another fuel cell technology is the proton exchange membrane fuel cell (PEMFC), the twin of a proton exchange membrane (PEM) electrolyzer which applies the same principles but in reverse. The conversion process is shown in Figure 3. In a fuel cell, molecular hydrogen is recombined with oxygen from the air to recover stored potential energy. The only emission from this process is water. The round-trip efficiency of an electrolyzer and fuel cell system is low compared to a battery; however, hydrogen can be transported more readily so is more appropriate for extended duration emergency power. Another fuel cell technology is the proton exchange membrane fuel cell (PEMFC), the twin of a proton exchange membrane (PEM) electrolyzer which applies the same principles but in reverse. The conversion process is shown in Figure 3. In a fuel cell, molecular hydrogen is recombined with oxygen from the air to recover stored potential energy. The only emission from this process is water. The round-trip efficiency of an electrolyzer and fuel cell system is low compared to a battery; however, hydrogen can be transported more readily so is more appropriate for extended duration emergency power.

**Figure 3.** Simplified schematics of a proton exchange membrane (PEM) electrolyzer cell and a proton exchange membrane fuel cell (PEMFC) during operation, showing hydrogen and electron flows. **Figure 3.** Simplified schematics of a proton exchange membrane (PEM) electrolyzer cell and a proton exchange membrane fuel cell (PEMFC) during operation, showing hydrogen and electron flows.

### 2.1.4. Renewable Energy Technologies 2.1.4. Renewable Energy Technologies

[28].

Renewable energy technologies integrated with digital grids are the new paradigm for electricity networks. Solar photovoltaic (PV) panels have become ubiquitous around the world and, accompanied by on- and off-shore wind turbines, are driving the transition to distributed non-fossil fuel based energy. Due to their solid-state nature, they require limited maintenance over their 25-year life, and economies of scale have resulted in spectacular cost reductions in recent years, which is continuing for large installations. Renewable energy technologies integrated with digital grids are the new paradigm for electricity networks. Solar photovoltaic (PV) panels have become ubiquitous around the world and, accompanied by on- and off-shore wind turbines, are driving the transition to distributed non-fossil fuel based energy. Due to their solid-state nature, they require limited maintenance over their 25-year life, and economies of scale have resulted in spectacular cost reductions in recent years, which is continuing for large installations.

Despite the potential for large hospitals, only 13 of the 695 public and 497 private hospitals in Australia have been identified as having installed mid-scale solar PV systems [27]. An industrial 850 kW rooftop solar installation for a hospital in New South Wales (NSW) can be expected to achieve a capacity factor of 17 percent [27]. High-quality large-scale renewable resources in Australia supplied through the grid can increase capacity to 30 percent and 45 percent for solar and wind, respectively Despite the potential for large hospitals, only 13 of the 695 public and 497 private hospitals in Australia have been identified as having installed mid-scale solar PV systems [27]. An industrial 850-kW rooftop solar installation for a hospital in New South Wales (NSW) can be expected to achieve a capacity factor of 17 percent [27]. High-quality large-scale renewable resources in Australia supplied through the grid can increase capacity to 30 percent and 45 percent for solar and wind, respectively [28].
