## 1 Introduction
Some sources suggest that the US military spends about $20.2 billion annually for air conditioning in Iraq and Afghanistan missions [7]. That amount included the cost of the fuel and the entire infrastructure involved in the delivery of the fuel to military camps.  
There are NATO initiatives in place on energy consumption in deployable military camps (tents) [8]. Tents are deemed as the most easily deployable solution. According to NATO Secretary General's Annual Report 2019 [9], the energy monitoring and camp simulation for energy efficiency is one of the modern-day challenges in overall energy security.  
In any of the aforementioned cases, temporary infrastructure is rapidly created to adapt to the enormous and quick influx of migrants or affected humans in need of immediate shelter and services such as communications, short-term hospitals, lighting, cooling of medicines, hot water and sterilization, all of which require energy [10; 11; 12]. Temporary camps are often converted into permanent settlements with inadequate long-term planning for operations and maintenance [13]. The main results of the study [14] show that about 7 million displaced people have electricity for 4 h a day in temporary camps. However, energy supply in displaced conditions is usually restricted to minimum survival requirements, with an estimated 90% of displaced people worldwide not having adequate access to electricity [15]. Due to the lack of funding and unsustainability of clean energy policies and practices in temporary refugee camps, current energy supply methods in these types of camps are ineffective, insecure for users and detrimental to the environment [10]. As the number of temporary camps and their longevity increases, there is a growing interest in renewable based energy supply systems that can improve access to energy and human comfort [15]. Renewable energy sources alone in the off-grid areas cannot currently ensure a sustainable supply of energy due to their inconsistent availability and strong dependence on environmental conditions [10]. Electricity supply in refugee camps is restricted to a critical HVAC system and electricity supply operation usually powered by diesel fuel generators [16; 17]. Currently, the most widely used renewable energy source is solar energy--it is safe, clean and easy to use, therefore it has become one of the most suitable energy sources that can be used in various fields and can be an alternative to fossil energy sources [18; 19; 20; 21; 22]. Many studies offer mobile PV systems solutions for autonomous electricity generation [23; 24; 25; 26]. With regard to temporary shelters, electricity is usually provided by off-grid solutions (diesel fuel generators), which are not a sustainable energy supply because of their dependence on fuel availability. Although there are no accurate reports on energy consumption data in refugee camps, the United Nations High Commissioner for Refugees (UNHCR) estimates that the annual expenditure on diesel fuel to produce electricity is more than $35 million [27]. Research [10] has provided examples of the energy related costs for two refugee camps in Burkina Faso and Kenya (see Table 1). These numbers show the need for safer, cleaner and more cost-effective access to energy. Efficient energy access in temporary structures is one of the ways to achieve the 2030 Agenda for Sustainable Development Goals [28], adopted by all United Nations Member States in 2015, specifically the third goal: good health and well-being (by means of comfortable microclimate in temporary camps); the fourth goal: quality education (by providing electricity for lighting); and the seventh goal: affordable and clean energy (by sustainable energy access). For successful implementation of expanding sustainable energy solutions in temporary shelters, the current paper presents a mobile energy unit with a renewable energy (PV) system for energy generation and HVAC systems operation.