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It is economically and practically feasible, to substitute 60% of the energy we use for cooling and heating our buildings with solar energy.



Cooling and heating our buildings accounts for 30% of global energy consumption (1). The vast majority of this energy comes from burning fuels with an impressive negative result on the environment  and economy (2).

Lighthouse Group  has developed a new patented method (8,9)  to collect the solar energy in the form of high temperature thermal energy.

The robotic Lighthouse Solar Collector (LSC) uses Fresnel lenses and solar tracking to concentrate the solar energy, and point focus to absorb it in the form of high temperature thermal energy, with high efficiency (>70%) even at high temperatures (4,5,6), without using  vacuum.

Up to now the available technology consists of photovoltaic PV ,  the classic flat plate thermal collectors and the evacuated tube thermal solar collectors (3). But these solutions do not address the problem effectively , and the use of solar energy in heating and cooling in buildings is less than 1% (13,14).

For the first time Fresnel lenses (and not concave mirrors) are used to concentrate the solar energy and  produce thermal energy that can support thermally driven applications (heating/cooling) in buildings at the local distributed level and, with double or triple efficiency than the current solar systems.

LSC can reduce the use of steam and chilled water of MIT’s campus buildings up to 60% with a payback period of less than 5 years , without government subsidy.

LSC coincides with the MIT’s Solar Center  intention to “explore new system concepts for concentrated solar power” as well as with the “evaluation and deployment of sustainable roof strategies” on the  roofs of MIT’s buildings that will be renewed  in the following years (12).

Moreover we are very much eager to share what we know and learn from others around the world  in order to fine tune our solution, as well as to use the demonstration capacity  of MIT to model, scale, and deploy the innovative concentrated Lighthouse Solar Collector  in a complex urban environment.


What actions do you propose?

97% of MIT’s Greenhouse Gas Emissions (11) comes from burning natural gas in its Cogeneration Plant  in order to support its buildings need for  electricity, steam and chilled water (10).

In order to achieve to reduce campus greenhouse gas emissions by at least 32% percent by 2030, one should concentrate to reduce and/or to replace the energy that the buildings consume for cooling and heating (steam and chilled water ).

We have also noticed from the Space Boundaries Maps and from Google maps that the buildings have a lot of space on their flat roof tops, with a general good South direction.

Towards this direction we have identified the following actions :

  1. Generally reduce the consumption of steam and chilled water locally in the buildings by producing on the spot heating and cooling using the energy from the sun and the LSC connected to absorption chiller  (Scope 1 of  GHG Protocol (11)).


  1. Supply heating from the sun to the distribution system in order to reduce the    need to operate the auxiliary boiler and the three Electric Driven Chillers or the need to purchase electricity , steam or chilled water (10)(Scope 2 of  GHG Protocol (11)).


  1. Supply  heating and cooling from the sun, to the buildings of the campus that are not connected to the  Cogeneration Plant (10,11) (Scope 3 of  GHG Protocol (11)) . Moreover supply heating and cooling to the transmission and distribution system in order to substitute  its losses with solar energy and not with burning gas (Scope 3 of  GHG Protocol (11)).


Action 1.

An adequate number of LSC are installed on the roof of the building that are connected to an absorption chiller. The LSC provides the thermal energy that is needed to the absorption chiller in order to produce the heating and cooling. The building uses the steam, and the chilled water from the cogeneration plant only when the power  provided from the LSC is not enough.

This way we achieve to  reduce the consumption of steam and chilled water directly from the buildings with decentralized production of heating and cooling, using solar energy.

Action 2.

An adequate number of LSC are installed on the roof of the buildings and are connected to the return lines of the steam towards the cogeneration plant and the heat exchanger (10).

The steam has a lower temperature after it has been used from the buildings. In order to gain some of the lost  temperature (thermal energy), it passes through  an array of LSC and returns to the cogeneration plant warmer (more thermal energy). As a result less energy is needed to prepare the steam again to be directed to the buildings or to the Steam Driven Chillers.

Depending on the weather  the need to burn gas in the auxiliary boiler will be reduced a lot.

If the collectors are placed near the cogeneration plant they can warm up again the steam used by the Steam Driven Chillers and this way reduce the need to use the 3 Electric Chillers (10). In this case the gains will be higher since the time of the big load (need for cooling in the buildings) is when the production of LSC will be higher. In other words the more warmer the weather is the higher is the demand for cooling , the higher is the production of LSC.

Action 3.

If the building is not connected with the Cogeneration Plant ( leased buildings), LSC can provide the thermal energy that is needed to  the absorption chiller. If the solar energy is not enough the absorption chiller burns natural gas that it is according to the plan to use only natural gas in the campus (12).

Moreover there can be peripheral installations of producing heat and chilled water from the sun using LSC and absorption chillers, that feed the transportation and distribution system. As a result  to substitute the losses of the distribution system with solar energy and add energy to the system (heat or chilled water to the system).

With the above actions and the available space on the buildings of MIT campus we believe we can substitute at least 15% of the thermal energy that is produced in the cogeneration plant from burning gas with solar energy, while maintaining all the merits of cogeneration (10).




As a general approach to the installation of LSC we should :

Assuming that the building is defined , with enough available flat rooftop and with a wet cooling or heating system (the cooling and heating is transferred to the building’s fan coil units and to the radiators with gold or hot water) we should :

  1. Measure or calculate the building’s energy losses, in order to  define the size of installation.
  2. Install adequate number of Lighthouse Solar Collectors (LSC) on the roof.

If it is to be used only for heating

  1. Connect the LSC to the current  heating system. Because the LSC can achieve high temperatures can be connected directly to the burner (petrol/gas) without the need of storage.


If  it is to be used for heating and cooling

  1. Install an Absorption Chiller of  adequate power.  The Absorption Chiller can produce heating and cooling and consumes gas not electricity.
  2. Connect the LSC directly to the Absorption Chiller and substitute the gas that it consumes to produce heating and cooling, with solar energy.


  1. Connect the whole system to a smart weather compensated  cooling/heating control system (the temperature of the fan coils will change depending how much cold/hot is the space inside the building and how cold/hot is the weather outside).


  1. Connect the whole system to the internet with Smart wireless sensors/switches (Bluetooth 4.1, wifi) so the students and potential users from all over the world can monitor how the system works, how much the greenhouse gases are reduced and how much money were saved and serve as a source of practical knowledge of using the solar energy for heating and cooling buildings.


The Lighthouse Solar Collectors with solar tracking are directed towards the sun from early in the morning until late at night. The Solar energy is concentrated through the Fresnel lens (front window)  on their absorber/heat exchanger  (high efficient because its small size and mass), that it gets very hot fast and the heating medium (water or oil) passes through it and the Absorption Chiller.

The heating medium is “preheated” and the Absorption chiller is using up to 60%  (without storage, the building itself can be used as a mean of storage) less gas in order to produce the same volume of heating or cooling.  

 Imagine during summer with so many hours of sunshine how much energy can be produced in the form of cooling.

The more intense sunshine and warm weather, the more the greenhouse emissions will be reduced and the most cooling will be produced substitute the Electric Driven Chillers (10) of the campus to a great extend and reducing a lot the GHG emissions(11)!

Our general direction is, to add energy to the 80% that is produced from the Cogeneration Plant (10), to minimize the need of the Auxiliary Boiler to produce steam and the use of the  3 Electric Driven Chillers to produce cooling (10). Our aim is  that the steam that is produced  in the Cogeneration Plant from the turbine that produces the electricity, to be enough together with the solar energy and the peripheral absorption chillers to cover the needs of the MIT campus and minimize the need  to purchase (electricity) or produce (burn gas) more energy.

We understand that the sizing and the placement of such an installation on the 100 and more campus buildings with different occupation levels and needs , is a big project by itself.

What can be done in the following months is a limited scale installation (LSC and absorption chiller connected to the heating/cooling system of a building) that will serve as an example and as a test bed for all buildings around the world, whether are connected to district heating and cooling systems or not.

Who will take these actions?

We have reached Technology Readiness Level of 7 according to NASA definitions (7)  and we have already perform test installations in house heating systems, where the potential problems in the moving base , solar tracking etc were identified and corrected (15).

We have also performed efficiency measurements in collaboration with the Hellenic Center for Scientific Research "Demokritos" (16).

We have also developed different models of the Lighthouse Solar Collector with different size Fresnel lens, bases etc., in order to match the needs of different buildings (15).

We are in a good position and we have the experience  to do the manufacturing even outside Greece , using manufacturers and related companies  in the area of MIT.

We need the help of MIT to provide the space and the building with the Fan Coils and the Absorption Chiller equipment.

We also need the MIT to make the study and the sizing of the Installation as well as to provide labs and related equipment.

Further planning should be done in collaboration with MIT staff, students and faculty.

How much will emissions be reduced or sequestered vs. business as usual levels?

Considering that every 100 square meters of building needs  an average of 25 KW to maintain the indoor temperature steady and that we have available roof top  10 square meters (to install two 2 square meter LSC)
and we use Absorption Chiller to produce the heating and cooling with Coefficient of Production 0.8 , then we can achieve  60% reduction in the annual gas consumption.

25 KW x 365 days = 9125 KW x 1.25 (0.8 COP) = 11400 KW

                                                                                 or 9120 Kcal

                                                                                  or 36 Cubic feet of natural gas

So if only Absorption Chillers were used , 36 Cubic feet of natural Gas would be consumed  producing greenhouse gas.

With such an installation we could substitute  60% of these fuels with solar energy namely 21.6 Cubic feet of natural gas every year per 100 square meters of building.

The above are rough estimations and more study is required.

What are other key benefits?

Solar energy is an abundant source of energy that it is not exploited as much as it could, mainly because we receive a lot of energy from the sun but not “in the energy level that we need it”.

LSC makes it possible for everyone to have the power of the big Power Solar Plant (14) on his/her roof and this way reduce the cost for heating and cooling the building as well as to effectively protect the environment.

Such a solution can also be adjusted to fit applications in food industry like pasteurization, in pharmaceutical industry, paper industry (13) etc.

And last but not least can be effectively be used for water desalination and sterilization. Through boiling water, water is cleaned without the use of electricity and with a very low cost. Moreover the highly modular character of the Lighthouse Solar Collector , allows it to be used for personal use in remote places, such a Fresnel lens could be fitted in a backpack , to big installations to support the water demand of villages.

What are the proposal’s costs?

Lighthouse Solar Collector  has a small cost, assuming that there is an organized small production , a Lighthouse Solar Collector capable to support  up to 60% the cooling and the  heating of a 50 square meter building , will cost around 2.000 $.

Considering the price of fuels and generally the cost of energy around the world, its cost can be paid back in less than five years. With a small cost LSC transforms the building's roof  to a petrol or gas well.

Also there is a cost for the purchase of the absorption chiller that it should be considered , but again its cost is paid back in a short period, and the use of gas that it uses to produce the heating or cooling, relieves the cities electricity grid and reduces the emissions of green house gases.

Also there is a maintenance cost. Because the Lighthouse Solar Collector is an active system and not a passive one  like the solar collectors that we know up to know, it may need a maintenance schedule.

From the installation that we have already made we calculate that this cost will be in the range of some dollars per year per collector. It is designed  in a way that all parts to be easily replicable with a durable simple construction that can stand the wind and rain for years.

 We have also developed a fail proof solar tracking system without the use of calendars and GPS. Ideally the whole system could be connected , with a low cost to internet, in order  not only the good  operation to be monitored but also to  make corrective actions from a distance (for example correct the  orientation towards the sun, we have already develop such a system).

The connection to the internet can be used for advertising but also to increase people awareness towards solar energy and its real potential.

Time line

We have recognized the need of the buildings for thermal energy and the potential of the sun to provide it, when we patented (8,9)  the Lighthouse Solar collector back in 2006.

 At that time the focus was on photovoltaic system and the big need for heating and cooling of the buildings was neglected. Now the need of the buildings is characterized by the European Renewable Energy Council as “a sleeping giant” and is coming in focus at last  (3).

We expect that the use of solar energy in the buildings will be expanded rapidly, in terms that we can’t really estimate because there are millions of buildings all around the earth that could be benefited of the Lighthouse Solar collector (LSC).

What we know is that LSC can be easily manufactured from common raw materials, and electronics, can last for many years, and it can easily be manufactured and installed in different countries..

The technology needed to build and install such a system, is spread all around the world and there is no limitation in adopting this solution fast, and tackle effectively the climate change problem ,and other everyday problems like the cost of energy, the air quality inside the cities and the desalination and cleaning of water and others.

 It will be a matter of a couple of months to manufacture, install and connect Lighthouse Solar Collectors on the buildings of MIT, that can be a good example for all the world, of an efficient solution to a major energy and climate problem.

Related proposals










(9)  Hellenic Industrial Property Organization.

      Patent Number 1005662, 8/28/2006

      International Classification (INT. CL8): F24J 2/08, F24J 2/38, F24J    2/40, F24J 2/46.


(10)  “A Methodology for Assessing MIT's Energy Use Greenhouse        Gas Emissions “

         by  Tiffany Amber Groode   Massachusetts Institute of Technology          May 2004.

(11) “MIT GHG Inventory  Overview” Methodology, Boundaries,

        Scope  and Data Overview  December 2015

(12) “A Plan for Action on Climate Change”  October 21, 2015 

         A joint statement

(13)  “Solar Heating for Residential and Industrial Processes” MITEI-WP-2015-04


(14)  The Future of Solar Energy

        An Interdisciplinary MIT Study led by the MIT Energy Initiative