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Hybrid solar solution

This UK-designed and built solution is the first in the world to combine three different renewable energy solutions into a single efficient and reliable system able to meet the heating and hot water requirements of well-insulated homes.

Hybrid solar solution

In order to explain the great efficiencies the Hybrid Solar Solution provides in both financial and environmental terms we must first take a step back and look at the three separate technologies used.

Photovoltaic panels (PV)

These electricity-producing panels have been available for several years and with the introduction of Feed in Tariffs are a very cost effective way of producing electricity and generating revenue. One little-mentioned drawback with PV is that as the surface temperature of the panel rises, the output drops.

Solar thermal collectors

Traditional solar thermal installations collect the sun's heat and convert this into hot water, typically meeting a property's summer hot water requirements. A major drawback is that in times of little or no sun there is little or no hot water.

Heat Pumps

Heat pump technology has been available for many years and installations of both ground-source and air-source systems are meeting heating demands all over the world. However, whilst these devices are potential greener than burning fossil fuels, they do still use large amounts of electricity.

The Hybrid Solar Solution

The Hybrid Solar Solution combines all three of the above technologies in such a way that the aggregate system outputs are far greater than those produced by the components individually.

How? PV, as already mentioned, has a linear drop-off in efficiency as the surface temperature of the panel rises. Given that PV panels are typically black and mounted in such a way as to get maximum exposure to the sun, this rise in panel temperature is inevitable. PV panels typically lose efficiency of up to 0.5% per degree rise in panel temperature. However the Hybrid Solar Solution combines both the PV and Thermal elements onto a single panel - a photovoltaic thermal (or PV-T) collector. This has two main advantages; firstly, by drawing heat away from the panel the electrical output is maintained at a higher level for a longer period, and secondly, with the PV and Thermal elements combined on a single panel less roof area is required, allowing for greater outputs on equivalent roof space.

Integrating Solar thermal and Heat Pump

The output of solar thermal is dependent on sunlight so for half the day and most of the winter a solar thermal collector operates very inefficiently and the heat collected is often at a much lower temperature than that required for use in a house. With the integration of the heat pump, the output of the thermal collector is no longer directly related to the intensity of the sun and therefore a constant output temperature can be achieved irrespective of solar input.

This has two major advantages, heat can be collected from the panel at night as the surface of the panel will act as a thermal absorber rather than solar collector, and the temperature of water in the house can be set and achieved irrespective of levels of irradiance (sunshine).

The efficiency of a heat pump is normally shown as a COP (Coefficient of Performance). This is a simple calculation of electrical energy input versus thermal energy output. However, the COP of a heat pump changes across the seasons as the result of the seasonal drop in source temperature. In other words, as the input temperature of the source reduces (colder ambient ground or air conditions), and the difference between latent heat input and upgraded heat output rises, so the COP falls. Air-source heat pumps are most susceptible to this; when the ambient temperature drops to below freezing the COP will drop off dramatically. Ground source heat pumps are more stable and do not have such a wide spread of COP, due to the relative constancy of the energy source.

The Hybrid Solar Solution maximises the advantages of air-source (namely low cost) without the downside of extremely inefficient performance in freezing conditions. The Hybrid Solar Solution collects its heat from the PV-T panels, so even in winter, under direct sunlight, the panels will be providing an input temperature far greater than the ambient air temperature, and generally well above ground-source, particularly at the end of a harsh heating season when the ground may well have frozen. This means that the operating COP of the Hybrid Solution surpasses those of other domestic heat pump technologies.

Volther PowerVolt Technical Specifications

The Hybrid Solar Solution uses a Volther PowerVolt Hybrid PV-T collector, which was the first MCS accredited PVT panel available in the UK (along with its sister product PowerTherm), providing the owner with revenue from both the Feed In Tariff and Renewable Heat Incentive systems for its respective electrical and thermal production.

The PowerVolt collector has been developed to maximise the electrical return of the panel, making it an enhanced PV collector, which also produces a reasonable amount of heat production in the summer, even without the heatpump.

The peak output for the Volther PowerVolt panel is 200/460 watts electrical/thermal respectively.When correctly installed the collector will produce more than 15% more electricity than conventional PV. When the heat pump is running the electrical output may increase by a further 25% under certain weather conditions.

Technical Specification of the Heat Pump

The Hybrid Solar Solution heat pump is a British-designed and manufactured unit available in multiple sizes all of which utilise Copeland scroll compressors. Through integration of the system with a PV-T array, and with a nominal input temperature of 20°C, the actual output of the heat pump will increase by approximately 33% relative to its nominal listed output. In other words, a heat pump with a nominal output of 4.5 KW will actually deliver a load (or duty) of 6 KW.

Hybrid Solar Solution Heat Pump nominal 4.5kw (actual 6kW)

50°C Leaving Temperatures

Water temperature (cold side) Duty (kW) COP *
19°C 5.96 3.94
20°C 6.05 3.98
21°C 6.17 4.04
22°C 6.35 4.15
23°C 6.55 4.28

* The COPs cited above are for the heat pump in its most basic form. Every unit we sell will incorporate an electricity frequency regulation unit which will improve efficiency by about 12% - we are currently conducting further lab-testing to fully substantiate this.

Each unit will also have an intelligent control system to optimise when and how the heat pump operates. This will further improve operational COP and reduce running costs.

Both of these efficiency measures, and others we are looking at, will be available on a retro-fit basis for customers who don't wish to wait the few weeks required to finalise the specifications.

In order to maximise the system efficiency the Hybrid Solar Solution control system works to pull heat from the array to the extent possible during daylight hours when minimal additional energy is required to recover it. With the use of appropriate heat storage a full 24 hours load can be covered. Clearly there will be times when the heating demand for a building cannot be met by the system alone; to cater for these rare occasions, and also to annul the risk of Legionnaires Disease, an immersion heater is included in the heating circuit.

In summary

The Hybrid Solar Solution is able to produce more electricity than PV, more reliable hot water than solar thermal, and heating at a better COP than most conventional heat pumps - all with little or no CO2 emissions.

Current projections suggest that a PV-T array will produce sufficient electricity over the course of the year to cover the demand of the heat pump, which will meet a reasonably insulated building's total annual heating and hot water requirements.Further to this the incorporation of a solar thermally charged ground loop increases the efficiency of the system to a point that it outperforms any heat pump based system.

This is the only integrated heating solution available on the market from which the owner can benefit from Feed In Tariff revenues whilst meeting the heating requirements of a building.

For high Code (5 & 6) new build developments, the Hybrid Solar Solution will deliver significantly more electricity than is required to power the heat pump and will contribute up to 50% of a house's annual electricity requirements.

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