How Natural Gas Supports Multi-Energy Integrated Energy Systems

As cities, industrial parks and large commercial developments pursue higher energy efficiency and lower carbon emissions, multi-energy integrated energy systems are becoming an increasingly important approach to energy planning.

Instead of relying on a single energy source, these systems combine different forms of energy — such as natural gas, electricity, district heating, heat pumps, solar energy and other renewable sources — to provide heating, cooling, electricity and domestic hot water according to changing demand.

Natural gas can play an important role in such systems because of its controllability, operational flexibility and ability to support combined cooling, heating and power generation.

The energy planning concept developed for Beijing Lize Financial Business District provides a useful technical reference for understanding how natural gas and other energy sources can be coordinated within a large urban energy system.

Energy Demand in Large Urban Developments

Large urban developments typically have complex and highly variable energy demands.

Commercial buildings, offices, hotels, hospitals, schools, residential buildings and data centers may require different combinations of heating, cooling, electricity and domestic hot water. Their energy consumption also changes significantly according to season, time of day and occupancy.

In the planning study for Beijing Lize Financial Business District, energy demand forecasting covered several major loads, including:

• space heating;

• air-conditioning cooling;

• domestic hot water;

• electrical power; and

• continuous cooling requirements for facilities such as data centers and computer rooms.

The planned development included approximately 5.36 million square meters of newly planned heating area and approximately 4.85 million square meters of cooling area.

The estimated heating and cooling loads demonstrated an important characteristic of large integrated energy projects: no single energy technology is necessarily optimal for every operating condition.

This creates the need for different energy sources and technologies to complement each other.

The Role of Natural Gas in a Multi-Energy System

Natural gas can provide a stable and controllable energy source within a multi-energy system.

Unlike some renewable energy sources whose output depends on weather conditions, natural gas-fired equipment can respond to changing energy demand and provide reliable energy when required.

Typical applications include:

• gas-fired boilers;

• gas engines and generator sets;

• combined heat and power (CHP) systems;

• combined cooling, heating and power (CCHP) systems; and

• industrial heating systems.

In a well-designed integrated energy system, natural gas does not necessarily operate independently. Instead, it can work together with electricity, heat pumps, solar energy, thermal storage and other energy sources.

This allows the overall system to select or combine different energy sources according to load, operating cost, efficiency and availability.

Combined Cooling, Heating and Power (CCHP)

One important application of natural gas in integrated energy systems is combined cooling, heating and power generation.

A natural gas engine or turbine first generates electricity. Heat contained in the exhaust gas and cooling system can then be recovered instead of being discharged directly into the environment.

The recovered thermal energy may be used for:

• building heating;

• domestic hot water;

• industrial process heating; or

• driving absorption chillers to produce cooling.

In the Beijing Lize planning concept, natural gas-fired internal combustion generator sets were combined with absorption refrigeration equipment to support cooling, heating and electricity generation.

The proposed configuration included three 2 MW natural gas-fired generator sets together with flue-gas and hot-water absorption units.

This type of configuration demonstrates how natural gas can provide multiple forms of useful energy from a single fuel source while supporting the wider energy network.

Integration with Heat Pumps and Renewable Energy

Natural gas can also operate alongside renewable and low-carbon energy technologies.

The Beijing Lize energy planning concept considered several complementary energy technologies.

Ground Source Heat Pumps

Ground source heat pumps can use relatively stable underground temperatures for heating and cooling.

They can provide part of the base heating or cooling load, while other energy sources respond to peak demand.

Sewage Source Heat Pumps

Where suitable wastewater resources are available, sewage source heat pumps can recover low-grade thermal energy and convert it into useful heating or cooling.

This can reduce the amount of conventional energy required by the overall system.

Solar Photovoltaic Power

Photovoltaic systems can generate electricity from available building roofs and other suitable surfaces.

Their output varies according to solar conditions, so they can be combined with controllable energy sources and grid electricity to improve overall energy flexibility.

Solar Thermal Energy

Solar thermal systems can contribute to domestic hot water production and other low-temperature thermal applications.

Auxiliary heating can then be provided when solar energy is insufficient.

The combination of these technologies illustrates the basic principle of a multi-energy system: different energy sources perform different functions and complement each other according to operating conditions.

Why the Natural Gas Supply System Matters

The performance of gas-fired equipment depends not only on the engine, boiler or burner itself.

Natural gas must be supplied at the required pressure, flow rate, temperature and cleanliness before it reaches downstream gas-consuming equipment.

A typical gas supply system may therefore require several treatment and control stages.

Gas Filtration and Separation

Pipeline gas may contain solid particles, liquid droplets or other contaminants.

Filters and separators help protect downstream regulators, meters, valves, burners and other equipment from contamination and damage.

Pressure Regulation

Gas supplied from a transmission or distribution pipeline may be at a pressure significantly higher than that required by the downstream equipment.

A pressure regulating system reduces and stabilizes the gas pressure according to the operating requirements of the gas-consuming equipment.

Depending on the project, multi-stage pressure reduction, standby regulating lines and automatic safety shut-off functions may also be required.

Gas Metering

Accurate gas flow measurement is important for energy management, operational monitoring and commercial accounting.

Gas metering equipment can therefore be integrated with pressure regulating and control systems according to project requirements.

Gas Heating

A significant pressure reduction can cause the gas temperature to decrease.

For applications where low gas temperature may affect downstream equipment or operating reliability, gas heating may be required before or during the pressure reduction process.

Safety and Control

Gas supply systems may incorporate pressure monitoring, temperature monitoring, flow measurement, emergency shutdown, gas detection and automatic control functions.

The exact configuration depends on the operating conditions and applicable project requirements.

Key Parameters for Designing a Natural Gas Supply System

Natural gas equipment for an integrated energy project should be engineered according to actual operating conditions rather than selected only by nominal pipeline size.

Important design information typically includes:

• gas composition;

• required gas flow rate;

• minimum, normal and maximum flow;

• inlet pressure range;

• required outlet pressure;

• gas inlet temperature;

• required outlet temperature;

• filtration requirements;

• metering accuracy;

• pressure reduction ratio;

• required redundancy;

• hazardous area classification;

• control and communication requirements; and

• applicable design codes and standards.

Load variation is particularly important in multi-energy systems.

When gas engines, boilers or other gas-consuming equipment operate according to changing heating, cooling and electrical demand, gas consumption may vary significantly. The pressure regulating and metering system therefore needs to maintain stable operation across the required flow range.

Gas Equipment for Integrated Energy Projects

Depending on the project configuration, the natural gas supply section of a multi-energy system may include:

• gas pressure regulating skids;

• gas pressure regulating and metering skids;

• gas filters;

• filter separators;

• gas heaters;

• heat exchangers;

• safety shut-off systems;

• flow metering equipment;

• control and monitoring systems; and

• gas odorization equipment where required.

These components can be integrated into a packaged or skid-mounted system according to the required gas capacity, inlet and outlet pressures, operating environment and project specifications.

HUAYI provides gas pressure regulating and metering equipment as well as gas treatment and auxiliary equipment for natural gas transmission, distribution and industrial gas applications.

Equipment configuration can be engineered according to different operating pressures, gas flow rates, temperature conditions and project requirements.

From Individual Equipment to an Integrated Gas Supply System

For engineering projects, selecting individual pieces of equipment is only part of the design process.

The interaction between filtration, heating, pressure regulation, metering, safety control and downstream gas consumption must also be considered.

For example, the required heater capacity may depend on the pressure reduction ratio and gas flow rate, while regulator selection depends on both inlet pressure variation and downstream operating requirements.

Similarly, filter and separator sizing should consider gas velocity, contaminant characteristics, pressure drop and required separation efficiency.

A system-level engineering approach helps ensure that individual components operate together reliably under normal, minimum and maximum operating conditions.

Conclusion

Multi-energy integrated energy systems combine multiple energy sources and technologies to improve energy efficiency, operational flexibility and supply reliability.

Natural gas can play an important role in these systems by providing controllable energy for electricity generation, heating, cooling and industrial processes while complementing renewable and other energy sources.

However, reliable operation of natural gas-fired equipment also depends on the upstream gas supply system.

Proper filtration, separation, heating, pressure regulation, metering, safety control and system integration are therefore important considerations when designing natural gas infrastructure for an integrated energy project.

By matching gas equipment configuration to actual flow rates, pressures, temperatures and operating requirements, engineers can create a more stable, efficient and flexible natural gas supply system.