Energy optimisation in data centres

Maximising the use of resources has become one of the current challenges for industry in an environment of increasing energy demand. There are areas with a high potential for optimising waste heat management, such as data centres, which have a high energy consumption. This heat can become a new energy opportunity that will eventually contribute to better control the operating costs of auxiliary power generation systems.  

The emergency power provided by generator sets in the event of a power failure is key in critical facilities such as data centres. In order to reduce the high energy consumption derived from the operation of the associated auxiliary systems, which represent fixed costs for the companies, we present an innovative solution that was born with the objective of taking advantage of the residual heat generated in these installations.  HIMOINSA and its engineering team have managed to integrate heat recovery into the core of its energy efficiency strategy, providing added value in terms of sustainability.  

The use of waste heat in diesel generators represents an opportunity to optimise the energy consumption of auxiliary equipment in critical installations, especially in adverse weather conditions such as winter. In the following, we analyse the consumption of different auxiliary components and how waste heat can become a key resource to reduce energy demand:

Main components of the consumption of auxiliary equipment 

1. Engine preheating 

This system is essential to ensure fast starting of the genset, as it keeps the engine at an optimal operating temperature even during the most severe environmental conditions. 

The 9 kW pre-heater, thermostatically regulated between 38 °C and 55 °C, consumes up to 96% of the total energy of the auxiliary equipment in winter. This high consumption is mainly due to the need to counteract heat losses in cold environments and the limited thermal insulation of the genset. 

2. Engine self-lubrication pumping system 

With a consumption of 1.5 kW for 5 minutes every 8 hours, this system ensures that the engine remains lubricated and ready for operation. Although its contribution to the total consumption is lower, it is still a load that could be partially covered by recovered energy. 

3. Battery chargers 

These devices keep the starter and auxiliary batteries in a continuous state of charge, with a consumption of 3 kWh per day. As these systems are in constant use, they represent a fixed energy load that can be mitigated with supplementary energy. 

4. Internal lighting 

Although it has a minor impact on total consumption (approximately 0.15 kWh/day), its relevance increases in applications where generators operate in isolated containers that need frequent monitoring or maintenance.

Total consumption in winter conditions 

In off-grid installations, the total consumption of auxiliary equipment reaches approximately 75 kWh per day during the winter. This high consumption represents a major challenge, as it requires a constant source of energy, even when the generator is not operating to supply main loads. 

Optimisation opportunities through heat recovery 

The waste heat generated by the genset while operating can be used to cover a large part of the energy needs of these auxiliary systems: 

• Engine preheating: 

Heat recovery directly from the exhaust system or generator cooling circuit can significantly reduce the consumption of the preheater. This waste heat can be channelled and stored to maintain the engine temperature in operating ranges without the need for the 9 kW electric heater. 

• Self-lubrication system: 

Temperature controlled through waste heat could reduce the frequency or duration of pumping operations, reducing their energy consumption. 

• Battery chargers: 

Although the consumption of chargers is relatively low, the use of energy derived from recovered heat to power auxiliary systems could free up grid or generator capacity, improving the overall efficiency of the system. 

Expected impact 

The implementation of a heat recovery system for auxiliary equipment could reduce the overall energy consumption of generators by up to 70-80% in certain climatic conditions. In addition, it improves operational sustainability by reducing dependence on external energy sources to maintain optimal equipment conditions.

PUE and heat emissions in data centres 

The Power Usage Effectiveness (PUE) benchmark is a metric used to determine the energy efficiency of a data centre, which generates heat as a by-product of its operations. Servers and other computer equipment convert electrical energy into heat while processing data. To prevent overheating, data centres use advanced cooling systems, which may include air conditioning, liquid cooling and other methods to dissipate heat. In this context and in terms of efficiency, an emergency power generator as a heat consumer with a heat recovery system is of interest. Some countries have regulations requiring the recovery and reuse of waste heat from data centres, which aim to promote energy efficiency and sustainability in the sector.  

Generator set heat exchanger as PUE optimization device 

PUE is determined by dividing the total amount of energy entering a data centre by the energy used to run the IT equipment it contains:

The PUE is expressed as a ratio, where the overall efficiency improves as the ratio decreases towards 1.0:

To reduce the contribution of the genset to the total power demand of the installation in an emergency genset application, a dual heat exchanger device is proposed for the HGY series, in addition to the traditional engine preheating resistor.  

The first circuit is integrated in series within the cooling system of the genset, while the second circuit is to be connected to the liquid phase CPD cooling system. The CPD cooling system functions as a hot circuit, and the genset circuit as a cold circuit.

Genset Heat Control Operative

To maximise the utilisation of the by-product heat generated by the DPC, it is proposed to implement an advanced temperature control system that operates as follows: 

1. Initial activation and regulation: when the control system is activated, the cooling circuit of the genset is stabilised at a suitable standby temperature by opening the hot circuit of the heat exchanger connected to the DPC. The system automatically regulates the genset temperature within a pre-set temperature range. This is achieved by controlling the OPEN/CLOSE status of the hot water valves coming from the DPC. 

2. Low temperature backup: If the heat exchanger is not transferring sufficient thermal energy to the genset and a drop below the configured threshold for the open temperature valve is detected, the engine pre-heater will be activated as an emergency system. This mechanism ensures continuity of heating and prevents the system temperature from dropping below optimal operating levels. (Impact on PUE: ↑↑↑↑) 

3. Overheating prevention: In case the temperature exceeds the upper limit of the preset band, the system will close the hot water inlet circuit to prevent heat backflow into the DPC, preserving both the efficiency and thermal stability of the system.

Solar energy as an auxiliary energy source 

Solar energy, as a renewable source, represents a sustainable solution to supplement the operation of diesel generators. This environmentally friendly method of power generation is useful for powering auxiliary devices in off-grid configurations, reducing the impact of constant power consumption on the PUE ratio of applications associated with emergency generator sets. 

Its implementation is directly dependent on the availability of solar irradiation at the DPC location, making it essential to assess the climatic conditions to maximise its efficiency.

Generator as an electricity consumer 

As mentioned, the generator requires a constant supply of 1.89 kWh per day to keep the auxiliary equipment of an HGY unit operational, in addition to the energy needed to power the traditional engine preheating resistor. This additional consumption increases the total energy demand, which has a negative impact on the PUE ratio of the DPC, affecting its overall efficiency.

Solar installation sizing criteria: Case of study: Madrid CDP 

In the northern hemisphere, the dimensioning of solar installations must take into account winter scenarios, as these represent the periods of lowest annual energy production. According to the PVGIS-SARAH2 database of the European Commission, historical measurements for Madrid show that the monthly horizontal irradiation reaches its minimum value in January, with 61.15 kWh/m². This data is key to designing systems that guarantee efficient performance even in conditions of low solar availability.

The availability of photovoltaic energy is given by:

Where G(β, α) is the total irradiance referred to a slope β and an azimuth angle α. It is calculated as the sum of: 

• Diffuse solar irradiance H (β, α), 

• Direct radiation D (β, α), 

• albedo radiation AL (β, α) contribution 

Calculating G(β, α) optimised for the winter season as β = latitude of location + 15oC and an azimuthal angle of 0oC, a daily energy availability of 4.86 kWh/m2 is estimated:

In the case analysed, an average solar availability of 4.86 hours per day is estimated for Madrid. This value, obtained from the conversion of units, is used as a reference for the sizing of photovoltaic systems. 

Considering a global yield of a photovoltaic installation with storage capacity R, which is given by:

All losses associated with energy conversion and storage are taken into account, including: battery degradation (kak_aka ), battery discharge effect (kbk_bkb ), inverter efficiency (kck_ckc ), cable losses (kvk_vkv ), autonomy in days (NNN) and battery deep discharge capacity (PdP_dPd ). 

For an HGY unit equipped with lithium-based batteries and an autonomy parameter of N=3N = 3N=3 days, the estimated system performance (RRR) is calculated at 71.3%. Including the energy consumption of the genset, this implies an energy input demand of 2.57 kWh/day. 

From the definition of peak power (PpP_pPp ), the number of PV modules required can be determined, considering an oversizing of 10%, using the following formula: 

Conclusions

Location of the system 

The location of the DPC is the starting point for assessing energy availability. Heat recovery and solar power generation systems require a design that takes into account aspects such as the layout of the piping and the location of the solar modules. It is important to install the system in an area that receives maximum solar irradiation, avoiding possible shading to ensure efficiency. 

Solar radiation and environmental conditions 

A critical factor for the installation of solar systems to support diesel generators is the solar radiation available in the area. This parameter directly determines the power generation capacity and, consequently, the number of solar panels needed to meet the demand. In addition, environmental pollution conditions can also affect and should be taken into account during design. 

Size and performance of solar panels 

 The size and performance of the solar panels are key elements in optimising the design of the installation. Higher panel output reduces the space required, while inadequate design may limit the ability of the system to integrate effectively into the DPC environment.  

Maintenance and logistics  

Heat recovery systems are designed to operate within a specific range of engine temperatures, which limits the amount of heat removed from the DPC. Although this can restrict heat transfer and the logistics of pumping and piping, the generator set is equipped with thermostatic valves that ensure efficient temperature control. All recovered heat is used efficiently, and occasional use of the traditional preheating resistor is minimal, contributing to a lower PUE. 

However, these systems require regular maintenance to ensure proper operation. Regular inspections of valves, pumps and connections are essential to maintain the efficiency and durability of the system.

Juan Manuel Tobal | Commercial Engineer at HIMOINSA - EMEA Region  

Juan Manuel Tobal Morales has a solid professional career in the energy solutions sector. An Industrial Engineer from the Polytechnic University of Cartagena, since June 2017 he has played a key role in the Power Solutions unit, managing operations and commercial strategies in the EMEA region (Europe, Middle East and Africa).   Throughout his career, he has led projects including those related to parallel emergency power units, such as the design and supply of the power solution for a data centre in Strasbourg, France. Juan Manuel Tobal has also led projects at the international airports of Lomé-Tokoin (Togo), Bobo-Dioulasso (Burkina Faso) and Bata (Equatorial Guinea). His experience and technical specialisation position him as a benchmark in the management of complex projects in global and critical environments. 

ABOUT HIMOINSA 

Founded in 1982, HIMOINSA is a leading designer and manufacturer of power technology solutions. It supplies power generation equipment in the international market: generator sets, lighting towers, and power storage and distribution systems.

From mission-critical to backup and continuous power, HIMOINSA provides complete, reliable and efficient diesel and gas power generation solutions wherever reliability is needed. With thousands of installations worldwide and different applications and sectors such as healthcare, hotels, data centres, manufacturing, mining, construction and independent power plants, the company has delivered power solutions for the international market during the last 4 decades ensuring cutting-edge technology, high performance, lower NOx, the most efficient systems and simplified maintenance.

In 2015, HIMOINSA became part of the Yanmar Group (Japan, 1912), a renowned company in the international market, a leader in the design and manufacture of industrial and marine engines, agricultural and construction equipment, etc. 

ABOUT  YANMAR

With beginnings in Osaka, Japan, in 1912, Yanmar was the first ever to succeed in making a compact diesel engine of a practical size in 1933. A pioneer in diesel engine technology, Yanmar is a global innovator in a wide range of industrial equipment, from small and large engines, agricultural machinery and facilities, construction equipment, energy systems, marine, to machine tools, and components — Yanmar’s global business operations span seven domains. 

On land, at sea, and in the city, Yanmar provides advanced solutions to the challenges customers face, towards realizing A Sustainable Future. For more details, please visit the official website of Yanmar Holdings Co., Ltd. 

If you have any queries, please do not hesitate to contact us: Marketing_Dpto@himoinsa.com