- Liquid fuels: why and why?
- Fuel purchase and storage
- The economic side of the issue
- The magic word “cogeneration”
- Equipment guide
Today we will once again touch upon the topic of choosing a method of heating a house. Cases when there are no other sources of heat besides diesel fuel are quite rare, nevertheless, such heating systems will be of interest not only to those who clearly need them, but also to simply interested people. Let’s talk about diesel boilers for heating a private house.
Liquid fuels: why and why?
One can argue for a long time about which type of energy is more profitable for heating, there will always be adherents of both the ideas of geothermal heating and conventional wood-burning stoves. The truth is that there is no uniquely winning option, it all depends on the goals and conditions of use of a particular system. So it is with diesel fuel: this rather archaic source of thermal energy still finds its use where there is no electricity or gas, and using a wood-burning boiler is considered even more archaism..
There may be several prerequisites for equipping a liquid fuel boiler house. The most important of them are a limited choice of energy carriers, free access to diesel fuel and a favorable price, sometimes the convenience factor is the dominant factor in comparison with other alternatives. It is not a good idea to evaluate energy resources solely by their cost and heating value. The costs of connecting to the backbone network, the price of the boiler unit itself and other components of the heating system are just some of the economic factors..
Although diesel fuel is in most cases second only to electricity in wastefulness, the difference in price can be covered by autonomy and ease of use. In any case, before finally settling on the choice of a diesel boiler, you need to understand what this heating system is like, what difficulties may arise during installation and operation, and also what hidden benefits may be. We will answer these questions.
Fuel purchase and storage
The first thing that makes oil boilers stand out in a negative light is fuel problems for them. To uninitiated readers it may seem that there is no problem storing several barrels of diesel fuel on the farm, but the illusion of simplicity melts when studying fuel consumption rates. For heating an average house of 100 m2 with standard thermal protection, 15 liters of diesel per day are required, that is, 2.5–3 tons during the entire heating season. And this is not at all a brutal expense: if the burner is incorrectly set up, poor insulation or due to installation flaws, the consumption may be 20-25% higher.
If such a consumption suits the economic indicators, it is necessary to provide delivery routes and a place for fuel storage. The most profitable and also the most difficult option is to order a fuel tanker, that is, to buy diesel fuel at wholesale prices. With such a purchase scheme, the savings can reach 10-15%, but there is a significant disadvantage – the inability to fit the entire volume of the tanker into its own storage. Hence the conclusion: the most tangible benefit from a wholesale purchase will be subject to a cooperative order, that is, if there are other farms nearby, heated by a diesel engine.
It is not recommended to purchase fuel “on the go”, that is, as it is consumed. Of course, the idea of acquiring a pair of 200-liter barrels looks more attractive than building a tank with a capacity of 3-4 m3, but this approach is extremely disadvantageous and unreliable. Seriously, the option of using consumable containers as the main ones should be considered only at temporary residence facilities: summer cottages, workshops or houses located in the immediate vicinity of a gas station. By the way, the best time to buy diesel fuel is the end of the first harvesting and sowing of winter crops in agriculture, that is, late summer – early autumn.
The construction of a fuel storage is the most difficult stage in the arrangement of a diesel heating system. In addition to a sufficiently high capacity, there are also requirements for tightness, chemical resistance, cleanliness and mechanical strength. The leakage of several tons of diesel fuel into the soil is a local ecological disaster. Therefore, for storing fuel, only factory-made metal and plastic containers can be used, certified by the manufacturer and certified for chemical inertness, cleanliness and tightness, as well as resistance to all kinds of influences..
There are two types of fuel storage: surface and underground. Since it is not profitable for the boiler to buy frost-resistant diesel fuel, preference is almost always given to the underground location of the tanks. So the fuel is reliably protected from overheating in the summer heat and at the same time is kept at a positive temperature during the entire heating period. The advantage of underground storage is also its high fire safety..
Let us briefly touch upon the issue of arranging an underground diesel fuel storage facility, which is regulated by GOST 1510–84 in terms of packaging. As regards the construction process, everything is ambiguous: on the one hand, there is SNiP 2.11.03-93, but warehouses with a total volume of up to 700 m3 do not fit into any of the categories described in this document. As practice shows, even carelessly installed underground storages up to 100 m3 without any problems pass the examination and acceptance, however, it is recommended to adhere to the above building standard (except for the values of the security zones), and also take into account the provisions of SNiP 11-35-76.
Since the shelf life of diesel fuel is 2–3 years and at the same time its calorific value is gradually decreasing, it is recommended to equip the storage facility from two containers. One of them must have a volume equal to or greater than the volume of the annual purchase, the other is intended to drain the surplus at the end of each heating season. Both tanks must be equally piped and equipped with a forward and reverse pumping system.
The economic side of the issue
The lack of gasification at the property is a very loose concept, often this problem can still be solved by paying a very specific price. The formula for determining the appropriateness and benefits of installing an oil heating system is extremely simple. It is necessary to compare the costs of equipping the fuel storage and boiler house with the total cost of gasification: the project, materials and fittings, the boiler unit itself. If the “balance” is negative, the installation of a diesel fuel boiler is considered unprofitable. If the result is positive, you need to divide the benefit by the difference in the cost of energy resources, taking into account their consumption. That is, in the case when the gain in price is leveled out after only 3-5 years of purchasing more expensive fuel, gas is usually preferred..
Dual-fuel boiler for operation on liquid or gaseous fuels
Let’s move on to specific examples. The cost of supplying gas to a non-gasified settlement can range from 500-700 thousand rubles when connected privately, and about 1.5-2 times less when connected in a cooperative manner. The cost of a tank for storing diesel fuel with a volume of 5 m3, which with a margin is enough to heat an area of 100 m2, is 110 thousand rubles. The cost of gas and diesel boilers is approximately comparable, but in the latter case, the installation of a pressure pump and a blower fan, as well as the installation of a transport pipeline, is required. All additional equipment for a diesel boiler house of this power class costs about 35-50 thousand rubles.
Real indicators of gas consumption for a house with standard insulation – an average of about 20 m3 per day for 180 days of the heating season, that is, 3600 m3 a year is almost 20 thousand rubles. In terms of calorific value, the combustion of a cubic meter of gas is comparable to the combustion of 0.65 kg of diesel fuel. Thus, about 2.5 tons are spent on heating, which costs a little more than 80 thousand rubles. In total, in order to go “to zero” at the total cost not earlier than 10 years, the cost of gas connection must be at least 600 thousand rubles. Naturally, with good insulation, the price difference will be less. Note that we neglect the rise in energy prices, since both gas and diesel are getting more expensive at roughly comparable rates..
The magic word “cogeneration”
People who intend to use diesel fuel should be aware that such an initiative can promise considerable savings. Under the condition of cogeneration of the heat of combustion of diesel fuel, the household is provided with practically free electricity. In a number of countries, surplus electricity can be discharged into the city grid at a common tariff.
How it works? Due to the higher density of combustion products, as well as due to imperfection of oil burners, the efficiency of diesel boilers rarely exceeds 70–80%. That is, from a quarter to a third of the energy generated in the boiler goes into the environment through the chimney. This problem in small thermal power plants is solved in several ways:
- the presence of an economizer that collects the residual heat of the exhaust gases;
- installation of Stirling engines in the heating block;
- using water from the engine cooling circuit in the heating system.
Gas piston power plant
Thus, with a total thermal power of 20 kW, the installation has a total efficiency of up to 95% and generates up to 7 kW of electricity per hour, which more than covers the needs of an average residential building, or even several.
In narrow circles, cogeneration power plants of this class are called micro-CHP. They cannot be found in online stores, while this equipment is in too little demand. However, the delivery of such installations to Russia and the CIS countries is possible; the companies Senertec, Tessari and WhisperGen are selling micro-CHP plants. Basically, these are gas piston power plants that use waste heat to heat water and supply liquid to the heating and hot water system. However, the calculation for operation on natural gas is not such a big problem, as a rule, equipment can be delivered in a diesel engine configuration. The average cost of an installation with an electrical capacity of 3.5-5 kW is 250-300 thousand rubles.
Simple diesel boilers do not differ much from gas boilers: the same water jacket, the same heating principle. For this reason, there is no obstacle to equipping a conventional flue gas boiler with a diesel burner. But even if the choice fell on a specialized boiler for operation on liquid fuel, we hasten to reassure you: no special tricks in the selection process are foreseen.
Like gas units, liquid fuel boilers mainly differ in the material of the heat exchanger and in the presence of a condensation chamber. Different models of boilers differ in individual indicators of efficiency and productivity, in this regard it is impossible to decide without a heat engineering project. Maintenance and operation of such a boiler is a separate issue, the main difficulties lie in the need to periodically clean the burner and combustion chamber from soot, as well as to carefully monitor the quality of the fuel.
The situation is a little more complicated with additional equipment. Unfortunately, it will not work to assemble a diesel heating system right off the bat: compatibility of different units and their compliance with operating conditions are too important. However, you should not give up: there are many standard projects of such boiler houses, besides, professional engineers will gladly perform design work at an average price of about 15–20 thousand rubles, plus 200–300 rubles for each kW of thermal power. Also, most specialists carry out field consultations at a cost that is an order of magnitude cheaper than the finished project, which is enough to select equipment and arrange a small heating system.