Introduction

Various worldwide sectors experience growing focus on issues of sustainable development and energy efficiency. The escalation of environmental problems and climate change encourages the search for new approaches to resource use. This trend is aimed to minimize harmful impacts on the environment. Renewable energy sources (RES) are one of the key technologies that help reduce carbon emissions. They also make energy supply safer and more independent from traditional fossil fuels.

Integrating RES into the design and construction of buildings allows for consideration of the climate and geographical characteristics of a specific region, maximizing the use of available natural resources. The use of solar panels, heat pumps, wind turbines, and other RES technologies in design helps reduce energy consumption from external sources and optimize operational costs. The development of energy-efficient buildings with integrated RES contributes to the creation of a comfortable and sustainable living and working environment.

Many worldwide countries successfully implement RES programs in construction and achieve significant results. Studying and analyzing the experience of other countries allows for the identification of effective approaches and practices that can be adapted in other regions. It is also important to take into account local specifics. The aim of this study is to explore international experience in integrating RES into building design and construction.

Main part. Methods of integrating RES into buildings

The integration of RES into buildings requires careful planning at all stages of design and construction. The use of modern technologies improves the energy efficiency of buildings and reduces their dependence on traditional energy sources. In 2023, clean energy resources provided about 41% of the electricity in the U.S. More than 16% of total generation came from wind and solar energy. These types are called «variable» RES due to their daily and seasonal fluctuations in availability [1]. Based on 2024 statistics [2], wind energy remains the most widely used type of renewable energy in the U.S. Recent years show a rise in solar energy usage, surpassing hydroelectric power and reaching a level above 870 trillion BTU (fig. 1).

Figure 1. U.S. renewables consumption, trillion Btu

Designing buildings with RES in mind begins with choosing architectural and engineering solutions aimed at minimizing energy demand. One of the key factors is building orientation. Optimal orientation maximizes the use of solar energy and minimizes heat loss. For buildings located in northern latitudes, it is recommended that windows and facades with maximum glazing face south to capture more solar heat during the winter months.

Effective building insulation plays a vital role in enhancing energy efficiency and reducing energy consumption. The use of modern thermal insulation materials in the building envelope (walls, roof, floors) and window systems minimizes heat loss, significantly reducing the need for additional heating. Solar panels and heat pumps reduce heat loss allows for more efficient use of generated energy and enable the building’s energy needs to be largely met by RES.

Solar panels (photovoltaic systems) are one of the most efficient ways to use renewable energy in buildings. They convert sunlight into electricity and reduce the building’s dependence on external energy sources. The efficiency of solar panels depends on the direction of installed devices. Maximum efficiency can be achieved by placing panels on roofs, facades, or other open areas that receive as much sunlight as possible throughout the day. The orientation of the panels typically depends on the building’s location. The optimal orientation is south with an angle that provides the maximum incidence of solar rays. To increase productivity, solar trackers can be used. These devices adjust the position of panels to follow the sun throughout the day. Although these systems increase installation costs, they can boost energy output by 35,91% [3].

In modern projects, solar panels are often integrated directly into the building’s architecture. This is known as Building Integrated Photovoltaics (BIPV). This technology enables the installation of solar modules on facades, roofs, and even in windows. Glass solar panels can be used in glazing and provide natural lighting and additional energy generation. Such integration improves the building’s energy performance and enhances aesthetics. It allows the panels to blend architecturally into the overall design of the building.

Heat pumps and geothermal systems are highly efficient methods of using RES for heating, cooling, and providing hot water to buildings. They use natural energy extracted from the air, water, or ground, which significantly reduces operating costs for energy resources and decreases greenhouse gas emissions.

Heat pumps operate on the reverse Carnot cycle. They use a compressor, evaporator, condenser, and expansion valve to transfer heat from the source to the building. These technologies can work in two modes. In heating mode, they extract heat from the environment and transfer it to the building’s heating system. In cooling mode, they remove heat from the building to the outside environment. This approach allows the same system to be used for both heating in winter and cooling in summer [4].

These technologies are becoming increasingly popular in the construction of residential and commercial buildings due to their efficiency and ability to integrate into existing engineering infrastructure. With proper design and installation of heat pumps and geothermal systems, a building can become almost entirely autonomous in terms of heating and cooling.

International experience in incorporation RES

The experience of various countries in integrating RES into building construction reveals effective approaches and methods that can be adapted and applied in other regions. Governments worldwide increasingly recognize the importance of integrating RES into the building sector to address environmental challenges and reduce greenhouse gas emissions [5]. Various policies are implemented to achieve these goals. They target both new constructions and existing buildings. Table 1 provides an overview of policies and measures implemented in the U.S. and Germany for comparison.

Table 1

Policies to encourage renewable energy in building [6]

The U.S. is one of the world leaders in implementing RES in building construction. In recent decades, numerous projects have been carried out across the country, aimed at creating sustainable buildings and improving energy efficiency.

The Bullitt Center is built in Seattle, Washington, and considered one of the most environmentally friendly commercial buildings in the world. The project was developed as part of the Living Building Challenge program. It includes strict requirements for energy efficiency and environmental sustainability. The building is equipped with a large photovoltaic installation on the roof that covers 100% of its electricity needs. The installed solar panels generate around 230 MWh per year. This fully meets the building’s energy requirements [7]. The Bullitt Center is equipped with a rainwater collection and wastewater recycling system. This method significantly reduces water consumption. The project demonstrates how the integration of RES can contribute to creating an energy-independent and environmentally sustainable office building.

Apple Park is an Apple’s headquarters in Cupertino, California. It is one of the most innovative buildings using RES. The building was designed to meet environmental standards and is fully powered by RES. Solar panels on the roof generate around 17 MW of electricity, as they cover a significant portion of its energy needs [8]. The building is also equipped with a geothermal heating and cooling system that maintains a comfortable temperature without using traditional air conditioning systems. Apple Park also incorporates energy storage systems and wastewater recycling, which reduces its environmental footprint and water consumption.

In the city of Freiburg, known as the «solar capital» of Germany, the Solar Settlement residential complex was built, consisting of 59 «passive houses» fully powered by RES [9]. The complex’s standard implies minimal energy consumption through high insulation and the use of RES. The buildings are equipped with solar panels on the roofs, which cover their own needs and allow excess electricity to be fed into the local grid. Each house is equipped with a heat recovery system and double glazing. This significantly reduces heat loss and the need for additional heating. The Solar Settlement project demonstrates the integration of the «passive house» standard and active implementation of RES.

The examples of the U.S. and Germany illustrate that successful integration of RES into buildings is possible at various levels. International experience in RES can serve as a model for the development and implementation of similar projects in other countries. In the future, it can contribute to the reduction of the carbon footprint and the enhancement of energy efficiency in the construction industry.

Conclusion

The integration of RES into building design and construction is an important step towards sustainable development. Modern technologies, such as solar panels, heat pumps, geothermal systems, make it possible to significantly reduce energy consumption and supply buildings with energy from environmentally friendly sources. The incorporation of RES in buildings enhances their energy efficiency and substantially reduces operating costs. This implementation makes these solutions economically beneficial in the long term. International experience, including examples from the U.S and Europe countries, shows that the use of RES in construction can be successfully adapted to various climatic and economic conditions.