- Basic thermal engineering concepts
- Basic methods to reduce heating costs
- Energy balance and insulation systems
- How to reduce the cost of electric heating
- Rationalization of fuel combustion
- Energy of the future
As the cost of energy resources rises, the issue of saving is increasingly being put at the forefront. Modern heating systems are designed with the expectation of rational consumption of energy carriers, for which many technologies have already been developed: both for insulation and for optimizing the operation of heating devices.
Basic thermal engineering concepts
The times when heating of housing was achieved at any cost without regard to resource consumption have long since sunk into oblivion. Energy reserves on the planet are becoming scarce every day, which is why mankind is forced to look for ways to reduce the cost of air conditioning technologies for the internal climate. However, it is impossible to implement such plans without having at least elementary concepts of how heat appears in our homes and why its supply has to be periodically replenished..
Looking ahead, we note an interesting fact: today there are houses in which heat losses are only 15–20 W per square meter per hour. You need to understand that we are talking about quite ordinary objects: at the moment, the development of the industry of building passive houses is a completely developed industry. To be more effective, let us note that the human body emits about 100-120 W of thermal energy even at rest. Thus, in a dwelling of a passive type, a person is able to maintain a comfortable temperature only by the fact of his existence. Of course, provided that the size of the room is limited to 5-7 m2, but add to this much more powerful heat sources that we are not used to noticing: refrigerator, personal computer, stove.
How is such an indicative energy balance achieved? It’s very simple: instead of pouring in innumerable portions of energy, we are fighting to reduce heat leaks from the building. At first glance, heat insulation on such a scale may seem unrealistic, but even half a century ago, in some refrigeration units, a degree of limitation of heat losses of about 3-5 W per square meter of enclosing structures was demonstrated, which can truly be called an impressive result. Today, these technological advances are increasingly being introduced into the practice of civil engineering..
But let’s move on to the topic of our discussion: how can we still ensure savings in heating buildings? In reality, there are only two ways to achieve this goal:
- make sure that as much energy as possible is converted into useful heat;
- limit heat leakage from confined spaces.
At first glance, everything is simple, but you will be surprised how varied can be the tricks that a person could implement in practice to achieve comfortable conditions in the environment of his stay.
Basic methods to reduce heating costs
Electricity can be called an ideal source of energy for heating, because it turns into heat almost completely, that is, the efficiency with such a conversion tends to 100%. However, there are also cheaper energy sources, such as gas, coal or fuel briquettes, but they do not realize their full potential during combustion, because some of the heat is carried out along with the combustion products. Devices that can collect this heat and transfer it to the interior of a building are called economizers. Due to their work, it is possible to significantly increase efficiency, while using cheaper fuel..
Of course, opportunities to reduce the heating requirement of a building should not be missed. Heat leaks through enclosing structures – walls, floors, roofs – can be significantly reduced by properly insulating them. Modern materials for insulation are significantly superior in thermal conductivity to building materials, for example, a 100 mm layer of expanded polystyrene is equivalent to a brick wall a meter thick. At the same time, the heat capacity of the insulation is an order of magnitude lower, it does not need to be preheated to room temperature.
Heat losses also occur during air exchange between the building and the outdoor atmosphere. For example, when opening the front door, up to 2–2.5 m penetrates into the room3 cold air, which can be avoided when installing an entrance sluice, that is, a vestibule. But in much larger volumes, heat leaves our homes through the ventilation system. And this problem can also be solved by total control over the supply and extract air volume. Devices, called recuperators, help transfer heat from the hood to the intake, thus heating the air entering the building. Also, the inflow can be heated when passing through a heat exchanger installed in the chimney.
We must not forget about natural sources of thermal energy. One of the most significant ways to save on heating costs is to properly organize natural light. This means an increase in the luminous flux from the south side of the building, the creation of wide openings in the attic roof or the formation of a cascade roof. It can be fairly noted that an increase in the proportion of glazing in enclosing structures leads to an increase in heat loss. Of course, you need to know when to stop in everything, but you can reduce heat leakage through windows, for example, by installing roller shutters or replacing double-glazed windows with better ones..
Energy balance and insulation systems
The topic of thermal protection of buildings is the most extensive and deserves a detailed discussion. Insulation systems are most easily viewed from the standpoint of energy balance – a concept that provides an assessment of all heat sources in a house, as well as all heat leakage paths. From this point of view, it becomes clear that high-quality insulation should be continuous along the entire perimeter of the building, including also the contact zone with the soil, and the abutment of the planes of different building structures to each other..
Two types of insulation systems can be considered: those that can be installed during the operation of the building and those that must be provided for by the construction project. Insulation of the floor and foundation can be cited as an illustrative example; these parts of the building can be provided with thermal protection only if there is open access to them, that is, it is at least easier to perform such work at the construction stage. Well, projects such as a heat-insulated Swedish (Finnish) slab are completely impossible to implement with the already finished base of the building..
Moving further, we are faced with the insulation of the basement and walls. These thermal protection elements can be installed even after the construction of the building, although with some reservations. For example, in order to ensure continuous insulation of the basement and the foundation, technological trenches around the foundation should not be backfilled. Accordingly, before the wall is insulated, it makes no sense to carry out finishing work..
But with the roof insulation system it is still more interesting. On the one hand, the completion of work on the thermal protection device can be postponed for several years, on the other hand, the possibilities for this should be provided for by the design of the rafter system and the Mauerlat. As a result, when the continuity of the entire insulation system is ensured, it is possible to calculate the specific dimensions of heat losses and predict the energy balance of the building..
How to reduce the cost of electric heating
There are widespread cases when additional possibilities of such heating are not realized when using electricity to heat buildings. As a first approximation, electricity is one of the most expensive energy sources for civilian use. However, upon closer examination, it turns out that in this way you can significantly save on heating. To understand how this is possible, you should familiarize yourself with the operating mode of the central power system..
It is rather difficult to predict the change in load during the day, at the same time, the operational regulation of the produced power seems to be an even more difficult task. In this regard, a tendency is born to stimulate electricity consumption during those hours when the total load on the network decreases. A kilowatt of electricity in the night tariff zone is 2.5-3 times cheaper than during peak and semi-peak loads, which creates an excellent opportunity to reduce heating costs.
The idea of multi-tariff daily consumption implies the accumulation of heat generated in eight hours of the night zone, with its subsequent use during downtime of the heating equipment. In buildings constructed of dense building materials with external thermal insulation, the function of heat accumulation is assumed by the building structures and interior items themselves. This is not always convenient, because during sleep the optimal air temperature for a person is 3-5 ° C lower than during wakefulness, moreover, not every house is able to keep warm for such a long time.
An alternative to this method of heat storage is the installation of a liquid heat accumulator. At night, an insulated container with water with a volume of 2-3 m3 heats up to the highest possible temperature, while the heat is supplied to the living quarters in sufficient volume. After the end of the night tariff, the coolant takes heat from the accumulator through the secondary heat exchanger and distributes it throughout the building. The operation of the system is simplified by the fact that during the period from 8 am to 4 pm, most residential buildings are uninhabited and it is not necessary to maintain the optimum temperature in them..
Rationalization of fuel combustion
Evaluating the efficiency of fuel combustion is another way to increase the efficiency of heating. Such an assessment can be made by analyzing the combustion products. Checking takes place in two stages: studying the chemical composition of flue gases and monitoring their temperature.
The chemical composition is established using portable gas analyzers. Special service organizations have this kind of equipment, therefore, the receipt of services will not be free, at the same time the analysis results can establish the fact of incomplete fuel combustion. Preliminary checks include an estimate of the concentration of carbon monoxide, but these measurements often do not reflect the real picture. For gas and diesel boilers, it is imperative to monitor the presence and concentration of hydrogen and methane, and for solid fuel – also sulfur dioxide and a wide range of hydrocarbons. The identification of these compounds in combustion products indicates the need to adjust the combustion mode or provide forced airflow..
Thermal analysis of combustion products is carried out mainly using pyrometric instruments. Measurements only at the outlet of the chimney do not give the required results, because it is necessary to monitor the temperature gradient along the entire length of the channel. If at the same time a large value of parasitic heat leaks is found, it is necessary to reduce the intensity of combustion or to equip the boiler room equipment with an economizer..
Energy of the future
The set of measures designed to reduce the cost of heating buildings is not limited to warming them and rationalizing the operation of the heating source. Modern technologies offer many effective solutions for obtaining energy from alternative sources: low-grade air heat, geothermal and solar.
You need to understand the inevitability of the final transition to such sources in the near future. Of course, one cannot say that modern alternative energy equipment can become a full-fledged replacement for existing heating installations, which have a much higher power class. Nevertheless, with due attention, such funds are able to cover at least part of the needs for heat and hot water, which is already good.
The first stage of such measures is to reduce the heat loss of the building, the second – to increase the efficiency of energy use. And only when these actions are of a general nature can we talk about the widespread introduction of heat pumps and solar collectors, designed to supply the human economy with practically free energy, albeit in limited quantities..