The use of renewable energy sources can ensure that the cost of barn climatization can remain low. Geothermal energy can certainly be an alternative here. Moreover, shallow geothermal energy can play an important role in maintaining summer comfort. Borehole thermal energy storage (BTES) uses vertical loops to exchange thermal energy. Aquifer thermal energy storage (ATES) systems use wells with extraction and injection of groundwater. It is prohibitively expensive to deploy classical compression cooling for this purpose. Geothermal energy offers opportunities to use passive cooling to also prevent overheating with minimal energy costs. As an alternative, smart active cooling with geothermal reversible heat pumps offers a solution to increase animal comfort and productivity up to an optimal level. 

Geothermal energy concept for Pig Farm in Belgium:
The research site of ILVO in Belgium (the Pig Farm) suits best for the integration of a central geothermal system with BTES. The barn is relatively young (recently built) and equipped with modern HVAC installations, consisting of radiant panels (twin tubes), floor heating combined with an extensive ventilation system. This installation can be relatively well adapted to integrate barn cooling. The geothermal system provides the necessary cold after a winter in which heating is mainly required. This cold is produced, without using compression cooling, purely by circulation through the ground and is therefore very efficient. In this project, passive cooling via twin tubes fitted in the air ducts can provide limited cooling capacity. Integrating smart use of the heat pumps, which provide year-round heat for piglet heating and hot tap water, allows active cooling by bringing the residual product of the heating into the stables as cooling during summer. 
When calculating total cost of ownership over 30 years, the dynamic payback time will be 10 years. Over the lifespan of the installation, a cost saving of 234,5 k€ can be achieved (-37%).

Smart control systems for livestock buildings offer a transformative solution for farmers seeking to improve the efficiency, welfare, and sustainability of their operations. Our work focuses on best practices for the installation of both indoor and outdoor systems that monitor and control vital elements such as temperature, humidity, lighting, and air quality in livestock environments.
By implementing these systems, farmers can reduce energy costs, enhance livestock welfare, and increase overall productivity. Automated controls allow for precise adjustments in real-time, ensuring optimal living conditions for livestock without requiring constant manual oversight. For example, the smart control system can automatically adjust ventilation based on humidity levels, reducing the risk of disease.
From a cost-benefit perspective, the initial investment in smart control systems is offset by long-term savings in energy consumption, reduced labor, and fewer losses due to health-related issues. Additionally, data generated from these systems helps farmers make informed decisions about resource allocation, animal health, and operational efficiency. 
Farmers adopting these smart technologies are better equipped to meet industry demands, reduce costs, and improve the welfare of their livestock, leading to a more sustainable and profitable future.
Smart control installation highlights in RES4LIVE
•    4 pilot farms (Belgium, Germany, Greece, Italy)
•    2 Swine farms, 1 Poultry farm, 1 Dairy farm
•    Environmental sensors (Weather stations, Temperature, Humidity, CO2, NH3, H2S, O2, VOC)
•    Energy consumption sensors
•    Integration with various systems (Heat Pump, PVT, Ventilation, Anemometers, Biogas)
•    Automation (Heat Pumps, Ventilation)
•    Alerts though a notification system

Intensive livestock farming consumes a considerable amount of thermal and electrical energy, especially in swine farms where piglets need heating all year round. Therefore, Photovoltaic thermal (PVT) collectors, that convert solar radiation into usable thermal (for hot water and space heating) and electrical energy are a promising form of renewable energy generation for agriculture and livestock farming specifically. A heat storage tank can be used to store excess heat during the day for use at night. To have available heat all year round, the PVTs can supply heat to a heat pump and thereby increasing the efficiency of the heat pump by up to two times. This was the case in the ILVO pilot farm in Belgium. PVT collectors can also be combined with a geothermal seasonal heat storage system to store excess heat during the summer for the winter. This is case in the Golinelli swine farm in Emilia-Romagna, Italy.
ILVO Swine Farm PVT System with Heat Pump Highlights 
•    24 Abora aH72 PVT collectors (45m2) were installed in combination with 2 heat pumps that deliver the final space and domestic hot water heat to the farm.
•    Expected annual solar heat supply to the farm of 15 MWh to 21 MWh with 24 Abora aH72 PVT collectors.
•    Expected annual electric PV supply to the farm of 4 MWh with 24 Abora aH72 PVT collectors.
•    Annual maintenance costs are less than 500 EUR.
•    With the heat pump and PVT installation, no gas is expected to be consumed by the farm all year round.
•    Expected return on investment is less than 8 years, which can be reduced with increasing gas and electricity prices as well as increasing price volatility.
Golinelli Swine Farm PVT System with Geothermal Storage and Heat Pump Highlights
•    24 Samster uninsulated PVT collectors (45m2) were installed in combination with a seasonal geothermal storage and heat pump to deliver the final space and domestic hot water heat to the farm.
•    Expected annual solar heat supply to the farm of 19 MWh to 25 MWh with 24 Samster PVT collectors.
•    Expected annual electric PV supply to the farm of 10 MWh with 24 Samster PVT collectors.
•    Annual maintenance costs are less than 300 EUR.
•    With the heat pump and PVT installation, no fossil fuels are expected to be consumed by the farm all year round.
•     Expected return on investment is less than 6 years, which can be reduced with increasing gas and electricity prices as well as increasing price volatility.

Intensive livestock farming consumes a considerable amount of thermal and electrical energy, especially in dairy farms where hot water is needed for cleaning the milk tanks, barn, and disinfection of the milking machines. Therefore, Photovoltaic thermal (PVT) collectors, that convert solar radiation into usable thermal and electrical energy are a promising form of renewable energy generation for agriculture and livestock farming specifically. A heat storage tank can be used to store excess heat during the day for use at night.
In dairy farms with milk storage, heat can be recovered from the milk chillers to pre-heat any water for domestic hot water use. It was decided to use high performing PVT collectors to further heat up the pre-heated water to the desired 60°C for hot water use in the farm.
LVAT Dairy Farm PVT Installation Highlights
•    24 Solarus concentrating PVT collectors (55 m2) were installed to take heat from the heat recovery system and further heat the water to the desired domestic hot water temperature for the farm.
•    Expected annual solar heat supply to the farm of 7.5 MWh with 24 Solarus PVT collectors.
•    Expected annual electric PV supply to the farm of 4 MWh with 24 Solarus PVT collectors.
•    Annual maintenance costs are less than 500 EUR.
•    With the heat recovery system and PVT installation, the e-boiler for domestic hot water is only expected to run during the winter for top up of heat.
•    Expected return on investment is less than 8 years, which can be reduced with increasing gas and electricity prices as well as increasing price volatility.

Transitioning to Renewable Energy Sources (RES) is vital for reducing the EU's livestock sector's environmental impact. Our initiative aims to decarbonize heating in European swine farms by integrating innovative dual-source heat pumps (DSHPs). These DSHPs are designed to replace traditional boilers for space heating and domestic hot water.
At a farrow-to-finish pig farm, two DSHPs replaced a 60 kW gas condensing boiler. The low-temperature (25 kW) provides floor heating at 42°C, while the high-temperature (40 kW) handles air heating and domestic hot water at 60°C. Combined with a photovoltaic thermal (PVT) system and a short-term thermal energy storage tank, the HPs achieve a higher Coefficient of Performance (COP). A dry cooler supplements the system when solar energy is inadequate. The system operated 85% in air-water mode and 15% in water-water mode, with average COPs were 2.95 for the high-temperature HP and 4.87 for the low-temperature HP in air-water mode, and 9.85 and 4.10, respectively, in water-water mode.

In a second pilot farm, a multi-source HP replaced a 34 kW LPG boiler for the nursery barn’s heating system. Here, PVT collectors are linked to a borehole thermal energy storage system, facilitating long-term heat storage. The HP utilized ambient heat via dry cooler. The HP maintained hallway temperatures near the setpoint, operating 17.4% of the time. It delivered 75% of its heat in ground mode and 25% in hybrid mode, with no air mode activation. The average COPs were 4.67 (ground), 3.50 (hybrid), and 4.34 (overall). This project offers valuable insights for practitioners seeking to adopt sustainable practices in livestock farming, demonstrating the feasibility and benefits of integrating RES technologies.

The goal of the Social Assessment (SA) was to evaluate the social impacts of deploying Renewable Energy Systems (RES) technologies in livestock operations across the four pilot farms involved in the RES4LIVE project. The SA is critical for assessing potential energy upgrades in livestock farms, as it offers a comprehensive understanding of the project's social effects on various stakeholders. This ensures that the benefits go beyond cost savings and environmental protection to include improved social outcomes, increased community acceptance, and greater sustainability.
The social assessment indicated that the overall SA Index remained positive across all scenarios and analyses.
Results from all farms showed that most participants had a generally quite positive perception of the farm's transparency in operations and reporting, particularly with regard to energy efficiency and emissions reduction. The most notable positive social impacts were observed in areas such as Environmental and Ethical considerations, Health and Safety, Human Rights, and Governance.
However, many workers reported no significant improvements in wages or compensation during the project interventions, despite an increase in workload and/or working hours due to the RES initiatives. Areas for improvement include providing more comprehensive training for farm personnel on the operation of new RES technologies to ensure the smooth running of farm operations. Additionally, efforts should be made to reduce disruptions during and after the installation of the systems.
This social impact analysis highlighted the positive effects of the RES4LIVE technologies and provided valuable insights, showing that future implementations of RES technologies can be better aligned with stakeholder expectations and lead to even more positive social outcomes.

In the pursuit of sustainable farming practices, integrating renewable energy systems can significantly improve operational efficiency. The environmental and economic impacts of an integrated system on an experimental swine farm in Belgium are assessed, suggesting that swine farmers could capitalize on potential benefits and utilize available funding opportunities to support implementation.
The system includes:
•    24 photovoltaic-thermal (PVT) collectors
•    Two multisource heat pumps, high-temperature (40 kW) and low-temperature (25 kW), equipped with a short-term heat storage tank
•    A smart control system
Compared to the existing system—a natural gas boiler for space heating and domestic hot water—the integration of the RES4LIVE system has the potential to reduce overall environmental burdens by 12%. Specifically, it can reduce the overall environmental burden caused by (i) ozone depletion by 19%, (ii) non-renewable fossil resource consumption by 17%, and (ii) the climate change impact category by 15%.

At the economic level, and considering subsidies ranging from 20% to 40% of the total investment cost, as a means to promote decarbonization at the EU level, the integrated renewable energy system can achieve a discounted payback period of approximately 13-14 years and 9-10 years, respectively. 
Therefore,  by incorporating similar interventions, swine farms in Belgium could enhance both their environmental and economic sustainability.

Adopting renewable energy systems (RES) can play a key role in improving the sustainability of farming practices. A study on a commercial swine farm in Italy evaluated the environmental and economic impacts of such a system in comparison to the system before installing RES, highlighting how swine farmers could benefit from available funding to support its implementation.
The system used includes:
•    A 7.68 kWel - 25 kWth photovoltaic-thermal (PVT) system
•    A multisource heat pump (35 kW)
•    A 30m borehole thermal energy storage system
•    A smart control system
When compared to the LPG boiler used before the project for heating the nursery barn of this farm, the RES4LIVE system could reduce the overall environmental burdens by 4%. This includes reducing the overall environmental burden caused by photochemical ozone formation (15%), non-renewable fossil resource consumption (15%), cancer-related human toxicity (13%), and climate change impact category (6%).

Economically, with EU subsidies covering either 20% or 40% of the total investment costs to support decarbonization, the discounted payback period for this system could range from 21-22 years in the former case, to 13-14 years in the latter.
Implementing similar systems on swine farms in Italy could improve both environmental and financial sustainability.

Integrating renewable energy sources (RES) systems into farming practices can greatly enhance operational efficiency and sustainability. This assessment examines the environmental and economic impacts of two innovative systems implemented on an experimental dairy cattle farm in Germany. The results suggest that cattle farmers can leverage these benefits and take advantage of available funding opportunities to support implementation.
The two systems evaluated are:
•    A biogas-to-biomethane upgrading plant, equipped with a BioCNG filling station
•    An adapted farm tractor for BioCNG use
The operation of the biogas-to-biomethane upgrading plant leads to remarkable diesel savings, causing a beneficial environmental effect equivalent to 4.6 times the total environmental burden of the biomethane supply chain system, only from the on-farm biomethane use in the retrofitted tractor. If all diesel savings are considered, including a potential sale of surplus BioCNG, the corresponding beneficial environmental effect could be increased up to 13 times.
The adapted tractor running on BioCNG offers additional environmental benefits compared to a conventional diesel tractor, reducing overall environmental burden by 9%, and the overall environmental burden caused by non-renewable fossil fuels and water consumption by 2 and 3 times, respectively.

From an economic standpoint, considering both the sale of BioCNG and fuel savings, the discounted payback period (DPBP) for the biogas-to-biomethane upgrading plant is 10 years. With subsidies covering 20% to 40% of the total investment costs, aimed at promoting decarbonization at the EU level, the DPBP could be shortened to around 8 to 5 years, respectively. After that, the DPBP for the adapted tractor would be around 2 years.
Incorporating similar interventions could improve the environmental and economic sustainability of cattle farms producing biogas in Germany.

Integrating renewable energy systems (RES) could play a crucial role in enhancing the sustainability of livestock farming practices. A study conducted on a small experimental egg-laying hen farm in Greece assessed the animal welfare and productivity performance of such a system in comparison to the one before implementing RES, highlighting the potential benefits for poultry farmers from available funding to support its adoption.
The system implemented includes:
•    A 9 kWp photovoltaic (PV) system to supply part of the farm’s energy needs
•    A 10 kW water-to-air heat pump for heating, cooling, and dehumidifying the indoor air
•    An LED lighting system tailored to the hens’ specific requirements
•    A smart control system, incorporating both environmental sensors and energy meters
Prior to the RES4LIVE project, the farm's relatively simple and outdated system consumed low amounts of energy. While the new system is more energy-intensive, it significantly improves the thermal comfort of the hens by regulating indoor air quality, temperature, and humidity compared to the previous setup. This leads to enhanced animal welfare, increased productivity, and lower mortality rates.

SYSTEM    PERFORMANCE PARAMETERS
Heat pump                 SCOPCooling     SCOPHeating
                                            3.12    3.77
Photovoltaics    Conversion efficiency
                                 10.4%
                            Self-Sufficiency (%)    Self-Consumption (%)
                                          22.81    84.12
Animal welfare and
productivity                   Decrease in mortality rate
                                           28% 
                 Increase in total egg production 10%    
Increase in average production per animal 19%
                                          
Although there is still much work to be done, adopting similar systems on poultry farms across Greece could improve animal welfare and productivity, with good potential of also improving their environmental and economic sustainability.

An integrated renewable energy system (RES) was designed and implemented for an experimental swine farm as a sustainable alternative to the fossil-fuel-based heating system. The RES setup includes 24 photovoltaic thermal (PVT) collectors, two modular heat pumps, and a thermal energy storage tank. The control system monitors the heat energy supply, while a network of sensors tracks environmental conditions. Monitoring and evaluation results highlight the system's efficiency and effectiveness in replacing the farm’s fossil fuel-based gas boilers, demonstrating the viability of this renewable solution for meeting the farm's heating needs.
     
The farm's heating requirements include air heating for the fattening pig compartments, floor heating for the farrowing compartments, and a combination of air and floor heating for the weaned piglet compartments. The entire heating demand is met year-round by the integrated renewable energy system (RES). Previously, a fossil-fuel gas boiler was used to heat circulating water to 70 °C for these needs. Now, two modular heat pumps have been installed: a high-temperature pump that heats the water to 62 °C and a low-temperature pump that heats it to 42°C. Additionally, the RES system offers a hybrid operation feature, allowing it to simultaneously utilize heat from both PVT panels and air sources, which enhances heating capacity and improves the system’s coefficient of performance.

Integrated RES system at ILVO swine farm
•    A PVT system with a solar station unit to generate 8.4 kWel electrical energy, and 32.8 kWth thermal energy.
•    Thermal energy storage tank that stores the thermal energy from the PVT that is used to increase the heat pump coefficient of performance. 
•    Two modular heat pumps
o    24.5 kW medium temperature 
o    39.5 kW high temperature
•    Smart control and sensor system. 

A sustainable heating system was developed for pig barns as an alternative to fossil-fuel-based ones. It consists specifically in an integrated Renewable Energy Source (RES) system incorporating a borehole thermal energy storage (BTES) and photovoltaic thermal (PVT) collectors, integrated with a Dual-Source Heat Pump (DSHP). A sophisticated control system was developed and implemented to monitor energy usage and environmental conditions. The results of pilot installation and experimental trials showed that a tailored mix of RES can be effectively established for a given livestock farm, leveraging the renewable resources prevalent in farming environments.

The heating load provided by the geothermal heat pump can rise the temperature of the radiant pipes up to 55°C, i.e. the operating temperature targeted with the previous fossil-based plant. The fundamental system architecture incorporates a dual-source heat pump featuring not only an air-cooled evaporator but also a heat exchanger for transferring heat with a water/glycol blend sourced from a sequence of PVT collectors connected to boreholes. The primary novelty of the system resides in its capability for hybrid operation, enabling simultaneous utilization of both ground-sourced and air-sourced heat, resulting in increased heating capacity and COP efficiency.

Integrated RES system
•    35 kW medium temperature heat pump;
•    A PVT system with a solar station, to provide electricity for the heat pump operation and the electric needs of the nursery barn with its 8 kWel electrical output, as well as thermal energy with its thermal output of 25 kWth;
•    Borehole Thermal Energy Storage (BTES) system that exploits both solar thermal energy and underground heat capacity to increase the heat pump efficiency by storing the excess heat from PVT;
•    Smart control system. 

For the defossilization of an experimental dairy cattle farm, renewable energy systems (RES) were combined to provide electrical power for various devices as well as to replace diesel-powered machines with ones that can use biomethane instead.
The RES on this farm include a biomethane upgrade plant, a former diesel tractor that was converted to run on compressed natural gas (CNG), a sensor-operated tube ventilation and cooling system for a dairy barn, and a set of photovoltaic thermal (PVT) panels with a heat storage tank.

The base for this was an existing biogas plant with a combined heat and power plant (CHP) that is already able to provide the farm with electrical power and sells excess electricity to the national grid. In addition, the CHP provides thermal energy for heating the farm’s office buildings. The biogas plant is fed with the slurry of the dairy cattle on the farm, and the dairy cows are housed in naturally ventilated barns. Since heat stress has become an issue in dairy cows increasingly, the barn was equipped with a combined tube ventilation and cooling system that operates sensor-based and detects climate conditions that lead to heat stress. Based on environmental sensors that track temperature, relative humidity, and gas concentrations in the barn, the natural ventilation of the barn is supported by injecting ambient air from outside the barn through ventilation tubes with exhaust nozzles above the lying cubicles and the feed table as soon as a first temperature threshold is exceeded. When the temperature rises further, additional ambient air can be pre-cooled in evaporative cooling pads and mixed into the ventilation airflow to drop the air outlet temperatures and mitigate heat stress conditions in the barn. The heat stress situations naturally are more prominent in the warmer half of the year, which allows the use of a PVT system as a synergy. The solar panels provide extra electricity at the time when it is needed for the barn climate system. In addition, the PVT system provides thermal energy that can be used to partly replace the boiler that supplies hot water that is regularly used e.g. for cleaning milking equipment.
The farm tractor that is regularly used to feed the dairy cattle had its diesel engine converted to now use CNG. The conversion process kept the tractor’s power level and improved the emission level. The CNG is provided by the biomethane upgrade plant that uses a single membrane and a dual-purpose compressor to concentrate the biogas to a methane content of at least 95 % and store the then-compressed gas at a pressure of 250 bar. The prototype scale plant already produces more than enough CNG to run a tractor.

Integrated RES systems at the LVAT dairy cow farm
•    A PVT system with a solar station providing an average electrical energy of 4.50 MWh per year and an average thermal energy of 24.75 MWh
•    Thermal energy short term storage tank with 1,500 L capacity
•    Prototype off-grid BioCNG upgrade plant with a capacity to produce up to 10 Nm³ h-1 CNG with at least 95 % methane content at a storage pressure of 250 bar, with on-farm filling station
•    A diesel farm tractor converted to use CNG from renewable sources
•    Sensor-controlled tube ventilation and cooling system for a dairy barn

Intensive livestock farming significantly contributes to greenhouse gas emissions due to its reliance on fossil fuels, especially for maintaining optimal conditions in livestock buildings. The transition to Renewable Energy Sources (RES) is essential for reducing the environmental impact of the EU's livestock sector. Our recent initiative aimed to decarbonize experimental laying hen facilities while enhancing animal welfare by integrating a RES system.
The farm was upgraded with an innovative heat pump (HP) for climate control and a solar photovoltaic (PV) system for power generation. A sensor-based monitoring system was implemented to collect data on the system's performance and indoor conditions over an extended period, focusing on both summer and winter seasons.
Preliminary results are promising. The installed HP effectively maintains adequate indoor air temperatures during heat waves, eliminating mortality and thereby improving animal welfare. Additionally, when paired with the PV system, it reduces electricity consumption from the grid by 20-23%. This reduction leads to significant CO2-eq savings, with approximately 688 kgCO2-eq in summer and 314 kgCO2-eq in winter.
During the testing and fine-tuning period, the HP achieved a Seasonal Coefficient of Performance of 2.42 in summer and 3.65 in winter. These findings underscore the potential for scaling up RES integration in commercial livestock facilities, demonstrating substantial benefits for both energy efficiency and animal welfare.
This project provides valuable insights for practitioners seeking to adopt sustainable practices in livestock farming, highlighting the feasibility and advantages of incorporating RES technologies.

Energy modelling of livestock houses has significantly advanced in recent years as enables a precise assessment of the energy consumption due to climate control systems, a major energy consumer in these facilities.
The developed simulation framework is designed to simulate the most relevant phenomena occurring inside livestock house:
•    Initialization module
•    Animal simulation module
•    Thermal balance module
•    Cooling ventilation module
•    Moisture balance module
In order to initiate the simulation input data from the user are required, including:
•    the geometrical 
and 
•    thermophysical properties, farming features, specifications of the climate control system, and outdoor weather conditions.
AUA, ILVO and Golinelli farm
An increasing number of customized energy models has been developed by implementing the simple hourly method of ISO 13790, based on the thermal–electrical analogy between the simulated livestock house and an equivalent electrical network with 5 resistance and 1 capacitance (5R1C). This method applied separately to the farms of our interest.
The AUA farm: Τhe building and its climate control system underwent extensive renovation as part of the RES4LIVE Project. At this farm the above method applied as described corresponding to the above overall thermal profile.
The ILVO farm: Pig production on this farm is carried out with a closed cycle the focus of the modelling activity in one of the fattening compartments. Below are the corresponding results.
The Golinelli farm: It operates a closed-cycle pig production system, managing all the stages. Τhe nursery barn is partitioned into three different thermal zones corresponding to a multi-zone calculation described below.
 

Computational Fluid Dynamics (CFD) is a promising technique to simultaneously obtain the fields of velocity, concentration, temperature, pressure and humidity ratio in livestock production barns over the entire computational domain, compared to field on-site measurements with limited measuring points. Although the distinct advantage of CFD modelling, one of challenges lies in the high requirement of computational compacity for large-scale livestock production buildings when the computational domain is wholly simulated with all geometrical detailed in the barns. This has limited the application of CFD modelling in study on sustainability and mitigation of heat stress and gaseous emissions from livestock buildings. Without proper prediction of those parameters, especially under the pressure of climate change, large uncertainties exist in assessment of the microclimate surrounding animals, which is highly related to the animal welfare and productivity, after new techniques are implemented for adaptive climatic barns.

In this context, we strive to predict the air speed, temperature and relative humidity around animals by adopting a domain decomposed technique to model the naturally ventilated barns by CFD in RES4LIVE project. As shown in the figure, the computational domain is decomposed into two domains, (1) the atmosphere domain plus the animal housing domain without detailed information inside the animal housing, and (2) the domain of animal housing with detailed information of housing configuration and animals. The parameters such as velocity, temperature, pressure etc. at openings of the animal housing achieved from modelling of domain (1) are used as boundary conditions for modelling of domain (2). This approach allows us to conduct CFD simulations with durable computational capacity and reasonable accuracy in predicting the velocity, temperature, humidity ratio surrounding animals. Thus, the technologies in preventing and alleviating heat stress, e.g., tube ventilation augmented with mechanical cooling developed within the context of RES4LIVE, can be evaluated with reasonable accuracy.

Heat stress in dairy cows occurs more frequently in recent years as an effect of global warming, also in moderate climate zones. Cows can begin to be affected even by ambient temperatures lower than 18 °C. This is not just an issue of animal welfare, but also has an impact on productivity of the cows.

Usually dairy cows in these latitudes are housed in naturally ventilated barns. In summer conditions these barns often require support in air exchange, which can be achieved by various kinds of fans. An alternative can be a tube ventilation system. In such a tube ventilation system tubes are mounted above the rows of lying cubicles in the barn as well as above the walkway at the feeding table. Air from outside the barn is pressed into these tubes with ventilators. The tubes come with air outlet jets that provide fresh ambient air to the barn and can increase air flow rates in the barn.

The tube ventilation system can be enhanced with a cooling option. This is realized with evaporative cooling pads, one per tube, that allow cooling down ambient air that is then transported to a bypass box, where the pre-cooled air can be mixed with ambient air for some temperature regulation. In RES4LIVE temperature drops of up to 5 K could be measured as a result of the maximum pre-cooling level, acting as a proof of concept. The barn climate system operates based on data from environmental sensors in the barn, like temperature and humidity loggers or gas concentration sensors.

A computer simulation of the airflow dynamics in a given barn is required as a prerequisite and ensures that the tube ventilation and cooling system is dimensioned adequately. Since the additional energy demand of this ventilation system (as other ventilation systems) is seasonal with peak demand during summer, these systems synergize very well with photovoltaic systems that provide their peak power in the same conditions where barn ventilation is required.

Farms that have a biogas plant have the option to further upgrade the biogas to biomethane that can be stored as compressed natural gas (CNG) and afterwards can be used as a fossil-free alternative fuel for heavy duty vehicles like tractors or trucks.
The production of biogas on livestock farms is usually based on using field residues, manure and slurry, which all are renewable non-fossil resources. Commonly the raw biogas that originates from the anaerobic digestion of these resources is converted into thermal and electric energy in a combined heat and power plant (CHP). Plant sizes between 100kWel and 250kWel are economically feasible in practice. As an alternative, the raw biogas can be purified into biomethane and compressed to 250 bar for use as a BioCNG fuel.

The prototype biomethane upgrading plant utilized in RES4LIVE uses a single-stage membrane purification process with the return of the separated CO2 to the digester next to the CHP operation for electricity and heat production. Between 10 and 20 % of the total volume flow of raw biogas can be used for CNG fuel, because this results in a CH4 reduction in the remaining raw gas stream for the CHP - the gas is diluted, and if the methane content is too low, the engine in the CHP might not work properly any more. As an example, a biogas plant with 200 kWel as a basic situation corresponds to a raw biogas volume of 100 Nm3 per hour. Economic feasibility starts in the range of 10 to 35 Nm³h-1 raw biogas that is purified into BioCNG fuel. For cost-saving purposes, the compressor used to push the biogas through the single-stage membrane separating CO2 and CH4 at the same time compresses the biomethane to a storage pressure of 250 bar. Drawing the CNG from the storage, the filling station works by pressure difference until pressure balance with the gas storage of the vehicle is achieved.

For the operation of a 35 m3h-1 raw biogas to BioCNG plant used at a capacity of 70 %, a full cost calculation results in fuel costs of 1.51 € kg-1 BioCNG. Any monetary benefits from GHG quotas from the production and use of biofuel have not yet been taken into account and can have an additional positive effect. This operating mode requires an adequate amount of consumers on-farm or also commercial or private consumers, which should be planned accordingly in a business model.

Borehole thermal energy storage systems represent an effective solution to increase the energy efficiency of renewable energy plants. Still, they generally have to comply with strict regulatory frameworks, mainly due to the deliberate modification of the subsoil's natural state. RES4LIVE involved the design, installation testing, and monitoring of a borehole thermal energy storage (BTES) system able to exploit the excess solar heat from photovoltaic thermal collectors (PVT).

A specific procedure was developed to allow the balance between the underground solar thermal storage and the geothermal heat extraction, in a specific climatic and geological context, to achieve an almost 100% exploitation of renewable energy.

BTES implementation in a pilot farm
Characterization of the underground properties and analyses over, according to the following phases:
•    investigation of geological, hydrogeological and geothermal conditions;
•    numerical modeling of the flow and heat underground transport;
•    Installation of test Borehole Heat Exchangers and dedicated piezometers;
•    Thermal Response Test and quantification of the potential heat storage
•    detailed design of the final system;
•    system installation in the farm, commissioning and activation.

BTES performances
The data measured during one year of testing and monitoring of the installed system showed the following results in terms of performances of the geothermal heat storage:
Underground seasonal storage of 40% of solar thermal energy producible through PVT panels;
•    Increase of COP of heat pump to heat a pig barn from 3 (air source mode) to 5 (geothermal source mode with BTES)
•    Replacement of a 34 kW LPG boiler with a heat pump requiring only 9 kWel, which can be provided by the same PVT used to feed then BTES.
•    Yearly emission reduction: 8621 kgCO2eq for a 840 m2 pig nursery barn.

As part of RES4LIVE, a diesel farm tractor was retrofitted to use biomethane as a compressed natural gas (CNG) and thus completely replacing a fossil fuel source with a renewable fuel source. The conversion process consisted of replacing the fuel tank with a high-pressure storage system for biomethane, changing the combustion by removing the diesel pump and injectors to replace them by spark plugs, ignition coils, and gas injectors controlled by an electronic unit (ECU). In addition, the cylinder head and the pistons needed to be machined, and the turbocharger had to be checked to operate well with the new setup. The feasibility of the retrofit for older tractors depends on the expected remaining life time, which should be at least 15 years. An adequate setup of the converted engine will keep the previous power level and improve exhaust emissions depending on the previous engine stage, although not as to reach the latest standard (EU 2016/1628 Stage V). The operation of the converted tractor requires access to CNG, which could be provided on-farm if a biogas plant along with a biomethane upgrade plant and filling station is available, or from a nearby CNG filling station. For maintenance technical staff that is trained to work with gas-operated vehicles or machines is required.

Livestock sector is a significant energy consumer of different energy carriers. According to Eurostat, about 158 million tons of cow milk is produced annually and on average, each kg of milk produced requires 3.42 MJ of energy inputs. From that number, about 74% accounts for feed production, 9% for diesel fuel used mainly for manure management, and 17% for other demands such as electrical energy for milking systems, feeding, lighting and ventilation. More specifically, it is estimated that the on-farm electrical consumption is associated with milk cooling (36%), milk harvesting (32%), water heating (23%) and water pumping (9%). There is a range of factors affecting the final results, the most important of which being the farm location, infrastructure, production system and type of milking system. Renewable energy sources and energy efficiency measures and technologies in combination with energy conservation practices provide a unique opportunity for farms to reduce energy consumption and produce their own clean energy to become partially or even totally self-sufficient. Solar energy, bioenergy, heat pumps, wind energy, geothermal energy and organic Rankine cycle applications hold great potential to be applied to all types of farms, covering an extremely wide range of energy needs. Within RES4LIVE, in a dairy pilot farm smart management and control will be utilized to efficiently control the heat and electricity production systems, and regulate the barn ventilation. A developed biogas upgrading unit will be also demonstrated on an existing biogas digester, as well as a retrofitted tractor for biomethane use. Moreover, an electric tractor will be used, charged by the electricity produced by photovoltaic thermal hybrid solar collectors.

The production of 1 kg of eggs requires about 20.5 to 23.5 MJ of energy inputs and in all cases at least 50% of all energy inputs are associated with the production of feed. On-farm energy demand is mainly covered by electricity (55%), followed by diesel fuel (33%) and LPG (12%). Electrical energy consumption can be further classified according to its specific use into ventilation (33%), automatic feeding (15%), lighting (15%) and packaging (14%); while diesel and LPG are used mainly for heating, but also incineration of dead layer birds. 
Renewable energy sources and energy efficiency measures and technologies in combination with energy conservation practices provide a unique opportunity for livestock farms to reduce energy consumption and produce their own clean energy to become partially or even totally self-sufficient. More specifically, solar energy can be utilized in all types of farms, being able to put up for both electricity and heating needs. Heat pumps’ potential is focused on applications that allow their coupling with photovoltaic-thermal hybrid solar collectors or geothermal units, especially in confined animal buildings, like poultry and pig farms. Wind energy constitutes a promising renewable energy sources for confined buildings, which have high electrical energy demand mainly for ventilation and lighting. 
Within RES4LIVE, photovoltaic panels will be installed to fully cover the needs of an experimental farm for egg production. A heat pump and inverter fans for ventilation will regulate its indoor environment along with a smart control system, which will also manage the photovoltaic power production for maximizing the self-consumption.

Agricultural machinery is almost universally powered by diesel fueled internal combustion engines, however, several farm machinery manufacturers have conducted research on their electrification and have showcased their electric tractor prototypes at various exhibitions. Conventionally sized field work tractors with battery electric drives offer: (a) reduced emissions, (b) increased driveline efficiency, (c) torque reserve, (d) lower fuel import dependency, (e)increased controllability and (f) use of renewable energy. 
Electric tractors can be either converted from conventional tractors, applying the appropriate modifications, or designed and manufactured from the beginning as electric vehicles. Currently the most applied concept for converting tractors is the replacement of the internal combustion engine with an electric drivetrain, without affecting the vehicle’s structure. Electric vehicles are classified into Battery Electric Vehicles (BEV) and Hybrid Electric Vehicles (HEV). HEVs use both an internal combustion engine and an electric motor and one of them acts as the primary power source. As current energy storage capacity of batteries is generally low to support several hours of heavy work, using an e-tractor would lead to a trade-off between either a longer working day for the driver due to the recharge time and reduced working time in the farm in total. At the moment two ways to overcome these limitations are autonomous drive systems and rapid recharging systems. Autonomous drive could allow the operation for more hours compared to a manned tractor, while rapid recharging could minimize the recharging time. RES4LIVE aims to demonstrate and assess the use of an e-tractor for on-farm daily tasks in one of its pilot farms.

Livestock farms consume a considerable amount of thermal and electrical energy. Photovoltaic thermal (PVT) collectors convert solar radiation into usable thermal and electrical energy, combining photovoltaic (PV) solar cells generating electricity, with a solar thermal collector, which transfers the excess heat from the PV module to a heat transfer fluid generating temperatures up to 80°C. Concentrating PVTs can reach temperatures up to 140°C. In a solar PV panel, photovoltaic cells typically reach an electrical efficiency (referring to the portion of energy in the form of sunlight that can be converted into electricity) between 15-20%, while the largest share of the solar spectrum (65-70%) is lost as heat, increasing the temperature of PV modules, thus decreasing the PV cell efficiency. PVT collectors make better use of the solar spectrum, supplying both electrical and thermal energy within the same area, while increasing the electrical efficiency. PVTs are especially interesting for applications where space is limited, combine the generation of electricity and heat in a single area, and can work most effectively with other energy sources such as heat pumps and coupled with thermal energy storage for provision when solar radiation is low. The average saved costs by PVT installation with available data is about 22 EUR/m2 annually. Investments of about 600 EUR/m2 are covered by saved fuel costs, considering the typical lifetime of a PVT system of at least 20 years, and reduce dependency on rising and fluctuating fossil fuel prices (depending on local feed in tariffs and prices for electricity, oil and gas, this value might vary a lot from case to case, See: Schubert, M. and Zenhäusern, D., 2020. Performance Assessment of Example PVT-Systems).

Energy use in pig farms can be assessed in the range 9.7-28.8 MJ/kg (Chen et al., 2015). Feed production is the largest energy consumer, with almost 72% of the total energy consumption whereas the remaining 28% is about direct on-farm energy use. Direct energy inputs are divided between transportation, heating, ventilation, watering, waste removal, lighting and other uses (such as mix and deliver feed, manure removal, mixing in slurry tanks, and power-washing). The key demand is due to the heating systems for the farrowing and first stage weaner houses and the mechanical ventilation systems. Therefore, pig barns show a significant potential of improvement of energy efficiency by means of a proper enhancement of the building envelope and the adoption of optimally controlled heating, cooling, and ventilation systems. Renewable energy sources and energy efficiency measures and technologies combined with energy conservation practices provide a unique opportunity for farms to reduce energy consumption and produce their own clean energy to become partially or even totally self-sufficient. More specifically, solar energy can be utilized in confined animal buildings, like poultry and pig farms, being able to put up for both electricity and heating needs. Heat pumps’ potential is focused on applications that allow their coupling with photovoltaic-thermal hybrid solar collectors or geothermal units. RES4LIVE aims to make the most of the significant de-fossilization potential of swine farms. Heat pumps will be demonstrated for both space and water heating applications. They will be also coupled with PVTs and geothermal heat storage, and smart control systems, which will monitor indoor environment and maximize the self-consumption.

The optimal thermal conditions for pigs are expressed as the thermo-neutral zone, which depends on the age of the pigs, but also on housing conditions, like air velocity, floor type, building insulation. Outside of this zone, cold or heat stress occurs, which results in discomfort, loss of productivity or even death. 
Lactating and gestating sows and heavy fattening pigs are most at risk for heat stress. It results in changed lying behaviour, decreased feed intake and increased respiratory rate, skin and rectal temperatures. The most important consequences on productivity are a lower body weight of the offspring, higher abortion rate, feed conversion and mortality. As the internal heat production of pigs has increased the past 50 years due to increase in leanness, modern day pigs are more susceptible to heat stress. Combined with global warming, heat stress is occurring more frequently and severely throughout Europe, leading to serious economic losses.
Cold stress on the other hand is most critical for young pigs, since they don’t have brown fat tissue yet, which produces heat at low temperatures. It is an important cause of piglet mortality, but also of increased feed intake without increased body weight, and decreased meat quality. 
It is very important to regularly check the actual ambient temperature in the pig pens and the pigs’ behaviour. Pay special attention to the new-borns, preventing cold stress, and to the sows and heavy fattening pigs, preventing heat stress. In RES4LIVE, the goal is to provide optimal comfort for the pigs with renewable energy systems and smart control. Heat pumps for example can provide both heating and cooling, which is vital for optimal productivity of the pigs.

The barn climate is a vital determinant of animal welfare and productivity. Ideally, the barn is climatized such that the heat produced during metabolism can be fully dissipated by the animal. When thermal balance is disturbed (by high ambient temperature or still air) certain physiological responses (panting, sweating) are triggered to adjust heat dissipation and/or production and restore the balance. Nevertheless, there is a limit to the efficacy of such responses, beyond which thermal stress occurs, leading to productivity loss and, in extreme cases, mortality. Dairy cattle are generally resistant to cold stress, but susceptible to heat stress, reportedly even at temperatures as low as 20°C. Heat stress is a significant challenge to sustainable dairy farming, especially in light of climate change and with continual genetic selection for higher productivity. Accurate criteria for when heat relief is needed remain the subject of ongoing scientific debate. In addition, while both practice and research have focused on the effects of temperature and humidity, there is growing awareness of the importance of air speed, with crucial implications for ventilation in dairy barns. In this context, RES4LIVE seeks to adapt and implement technologies that, while reducing reliance on fossil fuels, ensure effective prediction, prevention and mitigation of heat stress in dairy cattle as well. Data from pilot farms will be used to identify conditions of potential heat stress in various stages of growth and production. A smart control system will use these models for proactive control of the barn climate. The effectiveness of tube ventilation augmented with mechanical cooling of intake air in preventing and alleviating heat stress will be examined.

Agriculture 4.0 is the new approach towards farm management and precision agriculture. The ability to harness the technology advancements from other industries, such as IoT (Internet of Things), computer
science etc., allowed agricultural sector to evaluate and adopt them to achieve energy efficiency and optimal indoor conditions for the livestock. Agriculture 4.0 is combining low-cost sensors and actuators,
with cloud computing and artificial intelligence (AI) to achieve its goals and help farmers make better decisions, while at the same time reducing their environmental footprint.
Utilizing farmer-defined scenarios that consider specific livestock requirements, the areas occupancy and other characteristics, the IoT system is enabling smart control towards heating, cooling and ventilation
and optimize the microclimate, in terms of indoor air quality and thermal environment. To allow the smart control system to take the wheel and
operate automatically, the farms utilize smart sensors to
monitor the different environmental parameters,
such as temperature, relative humidity, wind speed and direction, hazardous gases (CO2, NH3, H2, O2, VOC), as well as energy consumption data. Moreover, the system can collect baseline data2 to evaluate, assess and compare “Before” and “After” conditions.
Precise indoor environmental and energy smart control are integral parts of the RES4LIVE implementation. The data will be available to the users in real-time, through a cloud platform, which will:
• allow remote monitoring;
• provide useful analytics, and;
• perform actual control of the connected devices.
The above-mentioned features will assist in both everyday operations and long-term farm management.

For homeothermic animals, thermoneutral zone is the range of ambient temperature in which normal metabolism provides enough heat to maintain an essentially constant body temperature. For laying hens this is between 10°C-25°C and is prerequisite for attaining maximum productivity. Raising hens outside these limits, initiates physiological responses that negatively affect performance and egg quality. Prolonged periods of heat stress are accompanied by reduced feed intake, reducing growth rate of pullets, and egg production and size for hens. Since birds cannot sweat, hens are panting at high temperatures to reduce their core temperature through mouth and the respiratory system. However, this physiological adaptation results in eggs with reduced eggshell strength and thickness and increased percentage of cracked or broken eggs. When hens are cold stressed, their feed intake increases in order to produce more metabolic heat and compensate with the heat losses from their body. This has unfavorable effects on feed utilization for growth, in case of pullets, and for egg production in case of laying hens, leading to increased costs. Moreover, during prolonged periods of cold stress, especially during night hours, small chickens are piling on top of each other, and a high incidence of mortality is usually observed because of suffocation. The negative effects of extreme temperatures are often combined with inadequate relative humidity and air velocity values. Therefore, in the framework of RES4LIVE, we deem of major importance the use of equipment that can accurately adjust microclimate conditions - heat pumps and smart control systems - in a laying hens house in order to attain maximum productivity with respect to animal welfare and egg quality.

Livestock buildings facilities need precise control of air temperature and relative humidity. In these demanding environments, the heat pump (HP) is the only indoor climate control technology that can ensure such conditions, since it is designed to provide heating, cooling, and dehumidifying in a space, by transferring thermal energy form a cooler space (source) to warmer space (sink) using electricity. 
They can draw energy from ambient air or water (coming from ground or solar collectors) to heat internal air (typical A/C heating mode) or provide hot water (35-50 oC). In cooling mode energy is extracted from hot spaces by circulating cold water or air with a piping system, in order to lower the comfort temperature of the animals (15-25 oC).
The efficiency of a heat pump is expressed in the COP value (Coefficient of Performance), which indicates how much electrical energy is needed to generate thermal energy.
Even though the heat pumps are powered by electricity (which may or may not have a renewable source), because of their high efficiency are considered a Renewable Energy Source (RES) technology, presenting no onsite emissions. A properly dimensioned heat pump (for a well-insulated space, about 0.09 kW/m2) can lead to cost savings up to 50-60% and a significantly lower environmental impact compared to a gas-fired installation for heating, and reduced CO2-eq. emissions. Their manufacturing specific cost can be of the order of 300-600 €/kWth, while they need limited maintenance.
Their capability of operating in heating, cooling, and dehumidifying mode, can provide superior thermal comfort of the hosted animals, leading to increased productivity with minimum climate change impact.