Our experience in the field of energy efficiency is more than 10 years. In our understanding, high energy efficiency is when the owner or user of a building pays as little as possible for utility resources such as electricity, heat, water, gas, and more.
Unfortunately, the Russian norms (СП 50.13330.2012 Thermal protection of buildings) regulate energy efficiency only in terms of heat saving by a building. Which often does not affect how much the user will ultimately pay.
In our work, we use international standards and practices to optimize utility costs. For example, standards such as ASHRAE 90.1-2016. This standard takes into account all aspects of the energy consumption of the building and the surrounding area and is continuously improved, updated every three years.
Building Energy Efficiency – 6 Steps
To achieve high energy efficiency, it is necessary to consider the building as a complex system. Energy optimization analysis goes from general to specific:
- Location and climate analysis
At this stage, we must evaluate the temperature graph throughout the year, maximum and minimum temperatures, humidity, solar radiation and wind rose. This data is essential for the analysis of specific architectural and engineering solutions.
- Load reduction
Secondly, we are engaged in reducing peak loads. The fact is that the total power of the equipment is selected precisely according to the maximum loads: thermal power, electrical, refrigeration. For example, reducing peak electrical demand can greatly save not only energy costs, but also the cost of connecting to the utility grid and the cost of installed equipment.
Traditional methods are used to reduce heat loads:
- Insulation of walls and roofs
- Window insulation
- Use of recuperation in air handling units
- Optimization of glazing area
- Sealing of enclosing structures
To reduce the power for air conditioning, you can use all the same solutions as for reducing the power for heating plus, the following:
- Selection of athermal glazing (Low-e, low-emission coating, sun protection)
- The use of shading and sun protection elements on windows and roof glazing (visors, lamellas – static and dynamic)
- Optimization of the glazing area, including on the roof.
- Determination of the premises and schedule of the building, in order to exclude premises that do not require air conditioning
- Selection of refrigeration equipment. For example, irrigated cooling towers operate in dry climates. They consume water, but at the same time they have a heat transfer rate many times higher. Also, the use of more efficient refrigeration machines can reduce the electrical load by up to two times.
- Use of free energy
Here we are talking about passive technologies for heating and air conditioning, ventilation and lighting.
For passive heating, you can use:
- Sunlight energy for building heating
- Building materials with high heat capacity, such as red brick or concrete. Such materials heat up when it is warm and cool for a long time when it is cool, or vice versa they work for cooling.
- Building orientation to maximize building solar heating.
For passive cooling, you can use:
- Natural ventilation when the temperature outside is lower than indoors
- Forced ventilation with ventilation units.
- Design natural ventilation or combined ventilation.
- Use evaporative cooling. For example, a fountain in the atrium or a special vertical shaft in which water is sprayed. The water evaporates, cooling the air. This solution works well in dry climates.
- Popular use of Free-cooling. To do this, the air conditioning system must be equipped with dry coolers that remove heat from the building without turning on the refrigeration machines when it is cooler outside than in the building.
A great effect on saving electrical energy is brought by the maximization of natural light. For this, it is provided:
- Skylights on the roof with an area of 4-5% of the roof area
- Glazing at a height of 2 meters
- Light shelves at the evacuation to increase the depth of penetration of light into the building
- Specially shaped ceiling
- Light colors of finishing materials (ceiling, walls, floor)
- Special solutions – light tubes or optical light guides.
- Efficiency of engineering systems
The next stage of optimization is the energy efficiency of engineering systems and specific components.
First of all, you need to pay attention to the following components:
- Hot water and steam boilers. Boiler efficiency ranges from 80% to 99%. For example, small condensing boilers have an efficiency of up to 99%. And good industrial ones are about 90%.
- Refrigerators and air conditioners. The larger the building, the more efficient the chillers must be. Presented here general case of energy efficiency of refrigeration machines from largest to smallest:
– Water-cooled centrifugal (centrifuge, turbocore, turbocompressors) –
– COP > 5.5(IPLV > 7)
– Water-cooled chillers (scroll, screw, piston)
– COP > 4.5 (IPLV > 6)
– Air-cooled chillers –
– COP > 3 (IPLV > 4)
– VRF COP > 3
– Split system
- Ventilation installations. Ventilation units consume electricity, heat and cold. To optimize electricity, you need to reduce the static pressure in the ducts, reducing the number of turns, increasing the cross-sectional area, reducing the length and number of devices in the channels. A premium electric motor with a fan is also selected. The integral indicator of the efficiency of the fan machine is the coefficient SFP (specific fan power). SFP shows how much energy the ventilation machine spends on moving 1 liter of air per second. Unit W / l * s. Also, to save heat and cold, the ventilation unit is equipped with a heat exchanger. Rotary is considered the most effective, then lamellar and glycol. Unfortunately, rotary can not be used everywhere, due to the fact that part of the exhaust air is mixed with the supply air. Even in ventilation systems, air economizer technology is used. This technology is rarely used in Russia. And in vain, since it is often very effective. The bottom line is that a ventilation machine uses outside air to cool or heat a building. For example, if it is cool in the building and it is warm outside, then the ventilation unit supplies warm air to the building, and vice versa, if it is hot in the building and it is cool outside, then the ventilation unit supplies cool air from the street into the building. This often happens in the off-season (autumn or spring)
- Lighting. The first step is to reduce the installed capacity. To do this, we use high-performance LED lamps (light-emitting diode lighting). The selection of fixtures must be made carefully with a margin of 20-30%. Since LED lights dim over time. Next, we use natural light and presence sensors. When there is enough light in the room or there are no people, the lighting turns off automatically.
- Heat pumps. Heat pumps, in fact, work the same way as air conditioners. A conventional air conditioner is an air source heat pump. If the system is turned on in the opposite direction, then it can heat the building. This solution can be effective in VRF systems or in central air conditioners in the off-season when the heating is turned off and the building needs to be heated. This is about 3-4 times more efficient than direct electrical heating. There are also heat pumps that use the heat of the earth or water. Such heat pumps pay off well if there is no cheap gas in the building. The system should be used for air conditioning in summer and for heating in winter. In this case, the heat pump gives the maximum economic effect.
- Energy recovery
A part of the building can be identified energy sources that can be put back into operation. We have already written above about recuperation in ventilation systems. It is also possible to equip the elevator with a regenerator, which will generate energy during the descent for its own needs.
If there is a large excess of heat in the building, for example, from technological processes (data centers, cooking, kitchen, etc.), then this heat can be used for heating.
There is also a recovery of sewage for preheating water for hot water supply.
- Renewable energy sources
After we have carried out a full-scale energy optimization, it is worth considering renewable energy sources. Renewable energy sources include:
- Solar power plant. Solar panels have come down in price a lot over the past three years. They also have high energy efficiency. For example, installing high-quality solar panels with 100 kW inverters in Moscow will cost you only 4,200,000 rubles. This system will generate about 100,000 kWh of energy per year. And the payback period of such a system will be 8-9 years.
- Wind generators. It makes sense to install wind turbines in two cases. The first is when there is a stable wind. The second is when you install an industrial wind generator with a capacity of 100 kW or more. Better than 1 MW. In our experience, low-power wind turbines have a fairly long payback period, and industrial ones have a payback period of 7 years or more. As a rule, large wind turbines have high energy efficiency.
- Solar collectors (solar systems). This system is used to heat water with the help of the sun. Water is heated on sunny days and stored in an insulated tank. Such a solution is especially effective if there are problems with connecting to gas, and the building uses a lot of energy for hot water supply, for example, small hotels on the Black Sea coast in the Krasnodar Territory or in the Crimea. The energy efficiency of solar collectors has been proven practically their experience in Mediterranean countries.
- Boilers for biomass/biofuel. If you have raw materials (furniture waste, agricultural waste, wood waste), then you can consider building a biomass boiler house.
- Hydroelectric power plants. Small hydroelectric power plants are also renewable energy sources.
- Geothermal stations. Geothermal plants are quite rare, but they are also renewable sources of energy.
By following this methodology to improve energy efficiency, you can greatly reduce energy costs. For example, it is possible to achieve an energy-neutral building, or a greenhouse-neutral building.
However, you can not apply all technologies at once and thoughtlessly. In order to evaluate architectural and engineering solutions in dynamics throughout the year, we build a digital twin of the building, on which we test various options and combinations of solutions.
Development of an Integrated Energy Supply and Energy Efficiency Strategy