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Condensed Heat - Optimization and scaling up of an energy efficient, long-during biomass condensation boiler with curved heat exchanger

Periodic Reporting for period 1 - C-HEAT (Condensed Heat - Optimization and scaling up of an energy efficient, long-during biomass condensation boiler with curved heat exchanger)

Reporting period: 2016-09-01 to 2017-02-28

The abrupt fall of the Brent Crude Oil price and, certainly, all its derivatives such as heating gas oil have caused a dramatic decrease of biomass boiler sales. The future of some of the best-known companies in this sector has been irreversibly altered and consequently some of the most important fossil fuel boiler manufacturers have finally dismissed the biomass division.
Other technologies for domestic heating (gas, oil-fired, electric or modern biomass boilers) are either unsuitable for moving towards a sustainable energy model, or insufficient in terms of energy efficiency. Whereas traditional boilers operate with fossil fuels, biomass boilers use a natural resource (pellets, wood chips, log). However, biomass heating appliances, although environmental friendly, perform inefficiently. Those few solid fuel condensing that have been developed have costly secondary heat recovery.
C-Heat have developed a cutting edge product based on sustainable feedstock (biomass pellets) being capable of working at low temperatures and built a biomass condensing boiler. C-Heat project consists of the development of the only biomass condensing boiler which needs no secondary heat recovers. Biocurve and Quintin have developed a biomass condensing boiler with a novel spiral heat exchanger and self-cleaning rotating burner which lead C-Heat to surpass from far the current state of art in terms of performance, (>10% than high-end average boilers), ripping design and price (at least 20% less than comparable solutions).
The objectives of C-Heat project are:
i. To redesign, improve and upscale of current portafolio (25kW and 100kW)
ii. To increase B&Q production capabilities
iii. To build a 25kW trasnportable demo to be used in fairs
iv. To install three C-Heat units in strategic locations
The experimental work done so far, is related with the work package 1, specifically this work package aims to enhance the current portfolio, that is, boilers from 25kW to 100kW in order to succeed at two major challenger: i) reduce cost of products for market and ii) improve the emission parameters for entering in strict markets as well as several minor improvements. In order to carry out these objectives we have redesigned the 25kW boiler and carried out Computational Fluid Dynamics (CFD) simulations studies of 25 kW heat exchanger. To do that, all simulations have been carried out by reducing the outside diameter of the heat exchanger to 470mm, in order to reduce the width of the boiler. The other proposed changes with respect to the current model have been the modification of the number of tubes, the number of holes in the water distributors (water jets), the shape of the tubes (circular / oval) and the shape of the outer shell (cylindrical / narrowed).
The cases simulated correspond to the condensing mode of the 25 kW boiler model of Biocurve at full load (25 kW output power). The results obtained in the simulation fit accurately with the results obtained experimentally in the actual 25 kW boiler. The BioCurve boiler heat exchanger has a very innovative design, since instead of straight tubes (usual in standard manufacturers), fumes pass through the inside of curved tubes. This allows for a large exchange surface within a noticeably reduced volume.
The simulations are only a first step in the design, so we have to validate them with the construction and testing of real prototypes. However, with the results obtained the conclusions are as follows:
- When reducing the outside diameter of the exchanger, it is advisable to increase the
number of holes in the water distributors (water jets), to reduce the water entry speed
and to avoid preferential paths in the flow.
- The best value obtained in the simulations corresponds to case 5, in which the tubes
instead of being circular are oval. The viability of its manufacture will be studied.
- The results with 4 shorter tubes are better than with 3 longer tubes. As the current model has 10 tubes, other configurations with 4 and 5 tubes will be simulated, as this will always
be a significant reduction compared to the current state.
- The results obtained will be used to obtain a first design of a boiler of lower power (15 kW)
and to study its possible incorporation to BioCurve boilers offer.
- This CFD tool will also be used to perform simulations on the remaining boilers of the
current BioCurve range (25-100 kW) for optimizing its design.

The following simulations to perform will be the following:
- Case 7: 4 tubes + 60 water jets + external Shell narrowed
- Case 8: 5 tubes + 60 water jets + external Shell narrowed
Bioenergy is a very dynamic sector, which represents over two thirds of the total renewable energy consumption in the EU. Across Europe, 17M Ha are sustainably harvested for bioenergy generation and the EU is the world leader (13.5Mio Ton in 2014, 45% of the global share). C-HEAT consortium has identified relevant market segments linked to this trend. As an industry segment, the heating sector is expect to grow at 4% CAGR, passing from a final energy consumption of 92.6Mtoe in 2010 to 138.3Mtoe in 2020. Therefore, positive trends for upcoming years, such as the forecasted CAGR ratios for biomass boiler installation or incentives to renewable can be noticed.
C-Heat 1